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Journal of the American Veterinary Medical Association

CONTENTS

Essentials of Veterinary Radiography—Raymond J.

Who’s Who at the Washington Convention...

Musea Domestica a Vector of Bovine Mastitis (Preliminary Report)—D.

Salmonella Food Poisoning an Infection—G. M. Dack

The Toxicity of Red-Stemmed Peavine (Astragalus Emoryanus) for Cattle, Sheep and Goats—Frank P. Mathews.......

Equine Pododermatitis—B. C. MeLean

Parasitic Skin Diseases in Dogs—A. R, Theobald

The Hematology of Avitaminosis A in Dogs and Rabbits—M. W. Emmel

Grasshopper-Poison Bait and Turkey-Poult Mortality—P. D. DeLay

A Case of Pseudotuberculosis in a Blackbird—F. R. Beaudette.

General Articles:

Clinical Data: Impotence in the Dog: Its Treatment with Male Hormone Substance—J. B. Engle and R. MacBrayer Pneumonia with Complications in a Cat Postmortem Digestion of the Stomach Acetonemia in Swine—F. E. Hull and A, F. Nolan.. Solar Dermatitis in a Heifer—Hugh F. Arundel Paralysis of the Penis of the Horse Directions for the Ascorbie Acid Therapy of Slow- Breeding Bulls—Paul H. Phillips 165 Chaulmoogrotherapy in Follicular Mange Case Report on Botulism Type C in Minks—E. R, Quortrup and A. L.

Surgery and Obstetrics: Preventing Flight in Birds by Tenotomy Jugular Phlebitis from Chloral ee: Meee ae me TAR 65 io ok os Soha ene Poh ew dee eeeedensiwnedaves ‘a Editorial With the Editors Current Literature The News Coming Meetings

Animals That Make the News

$5.00 per annum. Foreign $6.00; Canada $5.50 Single Copies 75 cts. prepaid in U

Published monthly at 600 8S. Michigan Ave., Chicago, IIL, by the American Veterinary Medical Association. Entered as Second Class Matte August 19, 1932, at the Post Office in Chicago, Illinois, under the act of March 3, 1879 Contents copyright 1940. Reproduction of any part of this publication is prohibited, unless special permission is given. Permission will be given if the purpose seems justiflable and in signed articles, if the rights or requests of the author are not violated thereby. Manuscripts are acknowledged on the same day they are received. Reprints should be ordered in advance. Prices will be quoted after publication, Please send prompt notice of change of ad dress, giving both old and new. Advise whether the change is temporary or permanent. Address all correspondence to American Vet erinary Medical Association.

OFFICERS: Capstun Way, President; A. E. Wight, President-Elect; L. A. Merillat, Executive Secretary; E B. iagmand, Acsictent Exec tive Secretary; M. Jacob, Treasurer.

EXECUTIVE BOARD: H. W. Jakeman, Chairman; C. W. Bower, Member-at-Large; A. E. Cameron, Ist District; J. G. Hardenbergh, 2" District; Herbert Lothe, 3rd District; W. E. Cotton, 4th District; H. C. H. Kernkamp, 5th District; I. E. Newsom, 6th District; Chas Seagraves, 7th District; L. J. Allen, 8th District; H. W. Jakeman, 9th District; O. V. Brumley, 10th District; Cassius Way, ex-officio; A. E. Wight, ex-officio.

BOARD OF GOVERNORS: H. W. Jakeman, Chairman; Cassius Way; A. E. Wight (— Committee on Journal),

EDITORIAL STAFF: L. A. Merillat, Editor; E. B. Ingmand, Assistant Editor; J. i) Shaffer, Editors’ Assistant; Associate Editors: J. Kk Beach, E. A. Benbrook, John B. Bryant, C. H. Case, James Farquharson, Ward Giltner, W. F. Guard, Raymond A. Kelser, J. A. 8. Millar, John R. Mohler, Chas. R. Schroeder, J. E, Shillinger.

FOREIGN LANGUAGE ABSTRACTING: Chas. H. Haasjes (Dutch), E. E. Hamann (German), A. G. Karlson (Scandinavian).

ii

Journal of the

American Veterinary Medical Association

600 S. Michigan Ave., Chicago, IIL.

Copyright 1940 by American Veterinary Medical Association

VOL. XCVII

AUGUST 1940

Essentials of Veterinary Radiography

By RAYMOND J. GARBUTT, D.V.M. New York, N. Y.

THE PATHWAY of the beginner in x-ray work is often difficult, as it frequently happens that he is not conversant with the technical side of radiology. In human medicine, where specialization has almost reached its zenith, the technician in charge of the x-ray department of the hospital’s laboratory is often well grounded in physics, radiography and _ radio-therapeu- tics. He is constantly making radiographs and processing them and, consequently, has acquired a high degree of efficiency. But this is not the case with the small animal practitioner because radiography repre- sents only one phase of his practice.

X-RAY TUBES

In order to understand the construction and action of an x-ray tube, a knowledge of its basie design is essential. The pres- ent-day tube is an improvement over the original type of hot cathode tube. It consists of a glass bulb which has been evacuated of atmospheric air. In the tube are placed two electrodes: the anode, or positive electrode, and the cathode, or nega- tive electrode, The cathode is the electrode through which the current enters the tube. The anode is the electrode by which the current leaves the tube. A stream of elec- trons, known as cathode rays, is produced at the cathode; these rays are capable of being deflected at the point of contact. A pencil of cathode rays is focused on the

target or anode. X-rays are given out in all directions in a plane determined by the angle and surface of the anode. X-rays are invisible and the pale-green fluorescence seen on the bulb of the old-type gas tube is due to cathode rays that are reflected from the anode and strike the glass wall of the bulb. Coolidge tubes and tubes of today in general show none of this fluores- cence, except when defective.

At one time the metallic part of x-ray tubes was made of platinum; however, it was found thai they would not stand up under prolonged use and large volume. Tungsten was substituted and it was dis- covered that tubes made of this material, if handled properly, have almost unlimited life. Copper is now used in most tubes and a small disc of tungsten is employed as a target in the anode face.

At the present time, the tube used most commonly in radiographic work is_ the radiator type. The copper anode extends several inches out of the end of the tube and supports a radiator composed of circu- lar or radial fins. It serves to conduct the heat out of the tube, thus keeping the tube from overheating. The high heat capacity of the copper bar and the cooling effect of the radiator are responsible to a large extent for the longevity of the modern x-ray tube.

The rotating anode tube is designed to permit the use of a much smaller focal spot

(101)

102

than.is’ possible with’ a ‘stdtionary anode. In this type the position of the cathode remains fixed in space while the anode revolves throughout the exposure to pro- vide continuously a fresh surface for the reception of the cathode electrons which are focused on the central pole of the anode.

TUNGSTEN TARGET FILAMENT

ACTUAL FOCAL a SPOT AREA

DIAGRAM OF BENSON FOCUS, SHOWING RELATION BETWEEN ACTUAL FOCAL SPOT

(AREA OF BOMBAROMENT)

AND EFFECTIVE FOCUS

AS PROJECTED FROM 20° ANODE

AREA OF

EFFECTIVE

FOCUS oil Diagram of line-focus tube.

Thus, the energy is distributed over the area of a broad ring and for the same exposure and conditions, the focal spot is only one sixth or less of that required in the stationary anode-type tubes. To secure the sharpest detail in a radiograph, it is always best to use the smallest focal spot tube permissible for the exposure.

The manufacturers of x-ray tubes fur- nish charts or tables indicating the kilo- voltages and milliamperages which may safely be applied at the various exposure times. The life of the tube will be pro- longed if the tube is operated within its rated capacity.

It must always be borne in mind that the tube is the determining factor in radiog- raphy and too great care can not be taken in handling it, in or out of use. Under no circumstance should the tube be jarred or the machine carelessly moved about.

CURRENT SUPPLY

The monly With

forms of current used most com- are the direct and the alternating. direct current a rotary converter

RAYMOND J. GARBUTT

Jour. A.V.M.A must be employed. This apparatus is expensive, requires maintenance necessitates the acquisition of an additiona] motor apparatus. If possible, the change from direct to alternating current should be made. While there may be an additional charge for changing the current, once it is changed the job is done for all time and the satisfaction of eliminating the converter is well worth the additional cost. When arranging for current supply either in a new or remodeled hospital, it is advisable to have installed cables of greater capacity than required at the time. The cost is not much more and if later a more powerful unit is required or an additional electrical

and

Diagram of round focal-spot tube.

unit is installed, the veterinarian will be assured that the cables and wires are heavs enough to avoid overloading and blowing fuses. It will be found advantageous to have a panel containing main switches: and fuses in or adjacent to the x-ray room, It is frequently possible to have the panel box recessed flush with the wall. Thus, much annoyance and delay may be avoided.

The x-ray room should have a number of double outlets rather than single ones. These will prove useful for lights and other electrical apparatus. The floor of the x-ra) room may be constructed of vitreous tile 01 cement; however, rubber tile, heavy lino-

op 1940 RADIOGRAPHY 103

eum, cork and plastic compounds stand up well, are sanitary and good insulators.

While various plasters have been recom- mended for plastering the walls of x-ray rooms to prevent x-ray leakage, most authorities agree that sheet lead is the only safe insulation. Sheet lead one-eighth in. thick is equivalent to several feet of brick or conerete in preventing rays from leaking through the wall. In applying sheet lead the seams should overlap and the nail heads should be lead capped.

Windows are essential for light and ventilation. They may be fitted with light- proof shades which can be made by a handyman or carpenter, or fitted by shade dealers who specialize in this work. They should be of durable material to withstand the continual raising and lowering.

An illuminator attached to the wall will prove useful in interpreting radiographs

Wall illuminator.

and in making comparisons with fluoro- scopic examinations,

One fault of most beginners is too-pro- lonved fluoroscopic examinations plus wide- open diaphragms, Thereby, secondary rays are increased and are picked up by the operator. If the diaphragm is kept as small as possible, the image is usually brighter. More than one tube has been vurned out in this manner. Short periods of examination, thereby allowing sufficient time for tube cooling, always should be

practiced. It should be borne in mind that the room must be well ventilated if ether is used for anesthesia. Under no circum- stances should ether anesthesia be employed if sparks are generated by the machine or if short circuits or loose wires are present.

7

Head fluoroscope.

PROTECTIVE MEASURES

Unless the patient is anesthetized, thie veterinarian doing radiographic and _ fluo- roscopic work is handicapped because of the resistance of the animal. Occasionally this will not occur with a docile patient, but many unanesthetized patients will show fear and apprehension by struggling. When in this condition, the patient must be held firmly. Because of the awkward ness and difficulty in holding the patient, attendants wearing heavy nonflexible gloves are apt to remove the lead gloves, which are worn for protection, and grasp the body or legs with their bare hands. The author has observed this practice innumerable times, in spite of frequent admonitions.

The veterinarian and attendants should use lead gloves on all occasions when x-ray- ing or fluoroscoping patients, especially when the hands come into the beam of direct radiation. The fact that the x-ray is invisible and unfelt and has the power of accumulating in the body should make one all the more cautious. Gloves of the mitten type made with no partitions for fingers or thumb are comfortable. In order to keep them open when not in use, and to permit airing, a wire frame may be made and inserted. Many veterinarians complain that handling dogs and cats with gloves on is difficult because the animals squirm and move about. It will never be

oR foe

104 RAYMOND J. GARBUTT JOUR. A.V.MA

remedied, however, until veterinarians as a group insist, with but few cases as excep- tions, upon anesthetizing patients before taking a radiograph and doing extensive fluoroscopy.

Often I have refused to take radiographs because the owner refused to permit the use of an anesthetic. If veterinarians would insist upon this before a_ radio- graphic examination, the public would soon become reconciled to the fact that anesthe- tization for radiography is necessary with dog and cat patients.

In placing a heavy dog on the x-ray table, one can stoop more easily when not wear- ing a heavy lead apron. Nevertheless, one should get into the habit of wearing a protective lead apron, and even in the heat of summer it should not be discarded while the x-ray is being used.

For large animal work, the portable machine is preferred. There are a number of different types on the market and the veterinarian will do well to investigate them all thoroughly before purchasing. It is necessary to determine if the machine will do the required work and it is essential to find out how long the company has been making the particular type of machine desired. Is it an outfit proved through trial and error? Will the company making it be in business when parts are needed? How long will it be before another model is placed on the market? Is it possible that the company making the unit might discontinue the manufacture of it because the demand is not great enough? In other words, will parts and service be available when needed? These questions must be determined by the purchaser.

Schnelle stated, “Don’t buy one of the older types of x-ray machines designed for human use.” I am in entire accord with this statement, having used an open-wire- type model for almost ten years prior to 1930. I can sympathize with the purchaser of this type of machine, as it is dangerous for the patient and operator alike. On several occasions while I was using our old model, severe shock resulted, which, while not serious, was extremely unpleasant. There are, however, many modern human- type converted machines which are service-

able. The author would suggest that the specialized veterinary types be thorough), investigated first.

STATIONARY TUBE STANDS

The stationary tube stand, which jg neither elevated nor lowered, but which js firmly fixed in one position or may move horizontally from left to right, is sold for veterinary use by several manufacturers Some of the units are provided with 4 series of elevated platforms, which can be raised or lowered in order to vary the dis- tance between tube and patient. Many veterinarians report excellent results with these outfits. However, there are other veterinarians who prefer the flexibility of the machine mounted on a stand which can be placed in any position above or under the table. The author has for a number of years used a table with a tube beneath and a tube above, the advantage being that for most fluoroscopic work the patient can be stretched out on the table top and exam- ined by looking through the screen. It is quite satisfactory for abdominal work, par- ticularly in large dogs. On the other hand, the small unit placed above the table may be adjusted to practically any angle and, because of its small focal-spot tube, it gives excellent detail.

One should realize in choosing an x-ra) that one machine will not do everything. Some sacrifice must be made if only one unit and one tube is to be used. In the case of portable machines the tube and transformer are usually contained in one unit. The tube is surrounded with oil, which serves as an insulator and keeps the tube cool. The lead-in wires are well in- sulated, thus making a shock-proof unit. The portable machine for large anima! or small animal work is ideal for taking radio- graphs which can not be taken at the veter- inarian’s office. However, much is sacri- ficed in portable units of all makes. There is little control of voltage, and high milli- amperage is not possible.

VOLTAGE AND MILLIAMPERAGE

The veterinarian should thoroughly understand the meaning of voltage and

ae |

Top (left): G-E model F-3. A compact and shock-proof office portable x-ray unit. This machine is capable of producing excellent radiographs of diagnostic quality and is the smallest practical unit

on the market today.

Top (right): Campbell two-tube unit. This machine has an x-ray tube under the table for fluoro-

scopy and a tube mounted over the table for radiography. The unit is shock-proof and easy to

operate.

Bottom (left): G-E model D-3 mobile x-ray unit. A feature of this model is simplified and ac- curate control of all radiographic factors. This unit is completely shock-proof, and ease of posi tion and economical operation are its outstanding advantages.

RAYMOND J. GARBUTT

milliamperage. Voltage is defined as the unit of E.M.F., or the force sufficient to cause a current of one ampere to flow against a resistance of one ohm. While this definition may mean much to the student of physics, it means little to the average veterinarian. However, when we say that the voltage in an x-ray machine means the power of penetration, or the factor neces- sary to provide penetration, the meaning of the term is clarified considerably. If we should need to x-ray the chest or spine of a large police dog or other heavy dog, we would need voltage to penetrate it.

A milliampere is defined as one one- thousandth part of an ampere. Like volt- age, the definition by itself means little, but when we say that it is the factor or force that cuts down the amount of time required to take a radiograph, its signifi- cance is understood.

Let us analyze the two factors of voltage and milliamperes as they apply to the veter- inary radiographer. Suppose he is called upon to x-ray the pelvis of a large dog. The patient has not been anesthetized and the veterinarian is anxious to obtain a rea- sonably clear radiograph. If he is using a portable machine of 10 milliamperes and 60 volts, the patient must remain quiet for a much longer period than if he were using a 30- or 50- or 100-milliampere ma- chine with 80 or 100 volts or more. It has been stated previously that the voltage controls penetration; therefore, with a large dog the operator needs considerable power of penetration, and the more voltage, the more penetration available. Thus, with sufficient controlled voltage, he can easily penetrate the pelvic bones.

Now we come to the practical utilization of milliamperage. With ample milliam- peres he could cut down the time materially. A 100-milliampere machine would permit him to take a radiograph ten times faster than a 10-milliampere machine.

If the patient remains quiet long enough, and by giving a long period of exposure, a good radiograph, even with a low milliam- pere machine, may be obtained. However, let us consider the positions of the human and the veterinary radiologists. The veteri-

Jour. A.V.)

narian’s patients, unless anesthetized, are for the most part inclined to shift and moy their position. This applies not only + the dog but to the larger animals as well Therefore, we need a machine that wil! penetrate deeply and quickly.

The question is often asked, why don’ the manufacturers increase voltage and milliamperes in portable machines? Thy answer is, it is impossible to do so and retain their size, portability and low cost.

FIXED VOLTAGE VS. CONTROLLED VOLTAGE

With fixed or partially fixed voltage th operator has one range of penetration or possibly one, two or three ranges, and 1 in-between, The three ranges are, of course. superior to the one range. However, a calibrated scale of control is far better. Why? Let’s take for example a small dog's or cat’s paw. We do not need great pene- tration, possibly 0.5 in. With controlled voltage, we can step down the penetration and not shoot the rays through as in the case of a 2- or 3-in. bone. The result is a clear radiograph which is not blurred by excessive penetration. I do not want to convey the impression that I do not recom- mend the portable unit, for it is necessary for certain types of work, but I do desire to point out the drawbacks of the portables. We can not expect as much from them for certain kinds of work as from the larger, stationary units. If you must use a port- able, purchase one by all means, but con- sider its limitations. The operating formula to remember is: Time + Voltage + Milli- amperes Radiograph.

THE DARK ROOM

The problem of building a_ processing room is not difficult if properly planned and designed for a new hospital. Many veteri- narians who have had to remodel and utilize limited space have, of course, a more diffi- cult problem. If possible, the room should be near the surgical ward or operating room. It should not be combined with the x-ray room, unless provided with suitable partitions and doors. It should be large enough to provide plenty of ventilation. which can be obtained by means of a blower

ver 1940

fan or by an upper and lower light-proof ventilator. If in a dusty section, the venti- may be more desirable than the blower fan. Excessive dust in the x-ray dark room is as undesirable as it is in the photographic dark room, and it should be avoided,

While the floors may be constructed of tile or cement, there are a number of plastic- type floors which will stand up well and are easier on the feet. To those who are con- templating building, I would advise them to write or visit the Architect’s Sample Cor- poration at 103 Park Ave., New York City. Here is assembled one of the greatest col- lections of different types of building mate- rials in the East. For the veterinarian considering remodeling or building, their services for equipment will prove useful. There is also available a set of books by

fators

Fan and motor unit dark room ventilator.

the Dodge Corporation, “Sweet’s Cata- logue.” A set of these splendidly illus- trated books costs approximately $130. If one can prevail on his architect to obtain a set of these books, they will prove helpful in choosing equipment, whether it be a loor for a dark room or hospital equipment. They contain several thousand illustrations.

The entrance to the dark room should be controlled by two doors spaced by a small vestibule. In addition to the tank for de- veloping and the hot and cold water faucets, there should also be a sink with hot and cold water. Cupboards for films and holders are necessary. These should be dust proof, but air should be permitted

RADIOGRAPHY

107 to circulate. Films should never be stored in a warm place or piled too close together, and when wet should be separated from each other and hung up.

If there is a window in the dark room, it should be provided with a proper light- proof shade or shutter. The bench for loading the cassettes or exposure should be placed away from the developing tank or sink; this is essential to avoid splashing and staining of holders, cassettes or films. A towel rack for either paper or cloth towels will prove advantageous. Film

holders

ETT ey |

ney) |

rm Cy

File cabinet for storing radiographs.

hangers for all of the different sizes of films which will be used should be attached to the wall. Hooks should be provided for hanging water-proof cloths and aprons. The inside door should be provided with a lock so that the door will not be suddenly opened, thus ruining exposed, undeveloped or unfixed film. If possible, a dryer should be installed.

It is important that the dark room be thoroughly painted. The floor, benches and walls, a few inches above tanks, should be thoroughly protected against the action of water and chemicals which may be splashed against them. For finishing the lower walls of the dark room, or processing room as it is often called, a paint such as Kodacoat may be used. It is black, non- inflammable, nonfogging, odorless, water- proof, and acid- and alkali-resistant. For

108

RAYMOND J. GARBUTT

Jour. A.V.M.A

the upper walls a panchromatic green paint* may be used. For the ceiling a white paint is indicated.

Frequently buildings will settle and cracks may appear; sometimes there is a shrinkage or contraction of walls and

Film storage chest.

spaces between the ceiling. These cracks should be carefully covered or filled so as to avoid light leakage on film storage.

LIGHTING IN THE DARK ROOM

The processing or dark room should be provided with adequate lighting facilities and, in so far as possible, the illumination

should be indirect. Indirect light boxes suspended from the ceiling should be used, and they may be painted to harmonize with the ceiling. Safelights should be installed over the loading bench and sink. A com- bination safelight and viewing box should be placed over the tank. The amount of light required depends upon the size of the room. Quite frequently one may desire to do photographic or camera work in the dark room, and for this purpose a series of two-way electrical outlets should be _ in- stalled. At some future time veterinarians may desire to photograph their radiographs to smaller sizes for purposes of reproduc- tion. If the room is large enough, it may be possible to set up a screen and try out moving pictures on the wall or screen. Splicing a film and making titles can usually be done more efficiently in a room

*Manufactured by Eastman Kodak Co., Rochester, N. Y.

of this kind. If one anticipates installing an enlarger or contact printer, an outlet should be placed near the space to be util- ized. Provision for additional changes should be ascertained in advance so as to eliminate cost and inconvenience at a later date.

TANKS VS. TRAYS

The beginner will frequently purchase trays because they are cheaper. If one’s radiographic work is limited or if it is impossible to install tanks, the trays may be justified. On the other hand, if his practice is growing and if he can afford it, he should purchase a tank. The first cost is smaller in the long run. While trays will suffice, there are a number of

Developing and fixing tank.

disadvantages in using them. To cite a few, trays are difficult to keep clean and are dust collectors which take up valuable room. Being bulky and made of porcelain, they frequently become chipped. With trays it is necessary to procure two large, dark bottles in which the solution must be kept. After the solution has been poured into the trays, it must be returned to the bottles. This means annoyance, labor and, to the busy practitioner, it may prove irksome. For a few additional dollars a tank may be obtained. With the tank once installed, the annoyance from the tray is eliminated. A tank left without covers soon becomes filled with dust and foreign particles, and the

sr 1940

and loses’ strength. may be made of stainless steel, composition or wood. The inside of the water section of the tank should be cleaned at least once a month to remove scum. Qecasionally one will observe a tank which has bulged on the sides and partitions. This is usually due to cleaning with boiling hot water. Boiling water should not be used in a composition tank, but in a soapstone tank it will do no harm. Because of its durability, cypress is generally used in the construction of wooden tanks. There are several manufacturers who either make cypress-wood tanks to order or carry them

developer oxidizes

Covers

in stock. The tank should hold Larger or smaller

Capacity of Tank.

from 2'4 to 5 gal.

Syphon attachment used in washing x-ray films.

sizes may be procured but the above should prove satisfactory for ordinary work. If the two faucets are hooked up together so as to discharge hot and cold water through one duct, a piece of hose should be attached to the pipe which leads into the water sec- the tank. The hose will prevent water from splashing around the dark room. A rubber hose also should be at- tached to the mixing pipe of the faucet over the sink.

The viewing illuminator always should be placed so that during the examination of radiographs the developing or fixing solutions will not contaminate each other. lf possible, it should be arranged so that the viewing screen is over the water or of the tank. The tank

tion of

rinsing seetion

RADIOGRAPHY

109 should be covered when not in use. If a solid cover is not available, particularly for the developing solutions, wax paper may be used. The ordinary roll-type used in the kitchen of the home is suitable, and may be cut to fit the inside of the tank and placed on top of the solution. <A pail to

Water flowing over top of hangers.

care for spoiled film and paper should be placed in a corner of the dark room. It may be made of porcelain, fiber or stainless steel.

Drainage. The tank may be drained from the center of the bottom or the mid- dle water or wash section. The develop- ing and fixing solutions empty into the water section by means of a hole in the partition, there being one hole in each sec- tion which is plugged with a cork. If the hole is properly plugged, there should be no leakage. Before the solutions are emptied into the wash section, the valve under the section is opened and the fluids are allowed to run off; the entire tank is then flushed out. With the tank supplied with three individual drain ducts, all three sections may be individually drained, cleaned and flushed.

SOLUTIONS

Solutions used for developing may be made by mixing the chemicals in the lab- oratory. It is more convenient, however, to purchase the prepared chemicals and mix with water according to directions. If

110

RAYMOND J. GARBUTT

the simple directions written on the con- tainer are carried out, there is no danger of error and there is a considerable saving of time. If the chemicals used are bought in bulk, there may be a slight saving, but the chance for making mistakes is too great for the average veterinary radiographer to take. In mixing the prepared solutions a clean stainless steel or enamelware pail should be used. If pails made of zinc, iron or copper are used, chemical changes take place which will fog the radiograph.

Interval timer and thermometer.

In some cities supply houses will call and remove the old developer and fixer and clean out the tank. They will then refill with fresh solutions. Not only do they sell the new solutions, but the old solution is put through a process and the silver is ex- tracted. This is a convenient service, although it is not always satisfactory, since many times no guarantee as to the quality of the solution is given. Care always must be taken in the dark room that when solu- tions are spilled, they are mopped up while wet. If permitted to dry, the particles will form dust which may settle on the films and screen and spoil them. The solution used in the developing process should last from one to two months, depending upon the amount of film developed and whether or not the tank is properly covered, and kept free from dilution with water or contami- nation with fixing solutions.

Temperature. —-It is important to test with a thermometer the temperature of solutions and rinse water before immersing films in the developer. This should be done particularly during extremes of

weather. The temperature of the wate and solutions should be 65° F. If the de. veloper or fixing solution is warmer, th, emulsion on the film will soften so that jj will wash off, leaving the film denuded of any image. Fogging and frilling of th film also may be caused by a high tempera- ture, that is, higher than 65° F. If th solutions are lower than 65° F., underde- velopment may result because the chemical] action is retarded. When it is impossih| to properly control the solutions withi: desirable limits, ice should be placed in th water or rinse section of the tank, or a: electric refrigerator should be employed. If it is not feasible to cool the solutions and wash water to 65° F., a number of precautions may be employed to process

Film loading safe.

films at higher temperatures. The develop- ing time should be shortened. The fixing time should be approximately 15 minutes and the washing time limited to 15 min- utes. The short development, thorough fixation and minimum time of washing al! help to prevent softening and swelling of the gelatin in the emulsion.

During hot months the time allowed for washing films should be as short as pos- sible, just sufficient for removing the fixing salts. Ice should never be placed in the developing tank or fixing tank as it will only dilute and contaminate the solutions: when ice is used, it should be placed only in the rinse solution. However, crushed

st 1940

RADIOGRAPHY

ice, placed in hermetically sealed rubber bags, may be used, provided there is no The bags should be placed in the

leakage. and fixing solutions and re-

developing

moved when the temperature is correct.

THERMOMETERS There are a number of thermometers which may be utilized for determining tem-

perature control. Most of them measure

First, attach the two bottom clips to the film.

about 6 in. in length, with a stainless steel back and a hook which may be hung over the side of the tank. For most work this type is suitable, but where a large volume of work is to be done, the author prefers the long wooden type with a large handle, which floats in the solution when released and will not sink.

FILMS

The passing of glass plates for x-ray work and the introduction of the modern x-ray film was an important step in ad- vancing x-ray development and technic. It was still further advanced with the intro- duction of the intensifying screens placed together, one in contact with each side of the sensitive film. Today, x-ray film is made of emulsion gelatin containing a silver compound and a blue-tinted, trans- parent cellulose-acetate base. When x-rays Strike this film, a change in its physical structure takes place. In view of the deli-

cate nature of the silver salt and gelatin, it is obvious that the emulsion is sensitive to light.

The changes which take place when the film is exposed to the x-ray can not be measured by any proved method, yet when placed in chemicals, called the developer, a definite reaction takes place which causes the tiny granules of silver to be deposited in the form of black metallic silver. It is

Next, attach the two spring clips at the top.

this silver suspended in gelatin on both sides of the base which forms the image. In radiography it is necessary to use a film which is suitable for recording, with suf- ficient contrast, slight variations in density in the part x-rayed. Besides fine gradua- tion and detail, it must show adequate con- trast in the finished radiograph.

In handling film care should be taken that the hands are clean and dry and that the chemicals have not been handled before touching the film; otherwise it may be- come contaminated. Care should be taken that films are not creased or buckled. Films should always be held at the corners and permitted to hang downward. Clean towels should be available. Particular care must be taken to keep the hands dry during the summer months.

Tree-like marks which are seen on films are due to pulling films too rapidly from cartons, exposure holders or cassettes, thereby causing electrical fric-

sometimes