U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.—BULLETIN No, 38. A. D. MELVIN, Cuter oF BUREAU. TUBERCULOSIS OFTHE IOOD-PRODUCING ANIMALS, BY D. E. SALMON, D. V. M. WASHINGTON: GOVERNMENT PRINTING OFFICE, 1906. Pong: wpti i Aa | r : ive’ 5 =i ay? U 4 7 i, so ba A an, s,s a Pe a ed iets - 4 7 = ig ; Wi nipay be 3 re .< Dy Sn, —_ cash, Py ae od - FF : - » i 4) ] eee 7 a Op =o nf . 7 ‘7 7 Mase) — a a. ee - Ceo DEPARTMENT OF AGRIGULTURE, BUREAU OF ANIMAL INDUSTRY.—BULLETIN No. 38. A. D. MELVIN, Cuter oF Bureau. Pe BeEkKCULOSTS OU EE FOOD-PRODUCING ANIMALS. BY D® Ee SALMON, D.-V. M. Wee i a ra St Sw OS AWN SS WASHINGTON: GOVERNMENT PRINTING OFFICE. 1906. > LETTER OF TRANSMITTAL. U.S. DEPARTMENT OF AGRICULTURE, Bureau or ANtMAL Inpustry, Washington, D. C., May 31, 1906. Str: T have the honor to transmit herewith a paper on Tuberculosis of the Food-Producing Animals, by Dr. D. E. Salmon, late Chief of this Bureau, who was especially engaged by you to prepare the same. IT recommend the publication of the paper as Bulletin No. 38 of this Bureau. Animal tuberculosis, though not nearly so prevalent in the United States as in most European countries, is nevertheless a serious prob- Jem and a menace to our live-stock industry, and is also regarded as a distinct source of danger to human health. Its infectious nature and the means for its repression should be fully understood, and earnest and intelligent efforts should be made with a view to its ultimate erad- ication from this country. The bulletin treats the subject in a very comprehensive manner and reviews some of the more important experimental work which has served to establish the facts and conclusions presented. The author is a recognized authority on the subject with which he deals, and the bulletin is written in the light of the latest scientific knowledge. The discussion of two phases of the tuberculosis problem which have received particular attention in recent years—the relation between the human and bovine forms of tuberculosis and the protection of cattle against tuberculosis by immunization—should be of especial interest at this time. respectfully, A. D. Metviy, Chief of Bureau. Hon. James WItson, Secretary of Agriculture. OC] SO | Y, D. of p, a CONDPENTS. Mga CATT Get eee nee ee eens wo =~ amine aininin ee civis~ === Part I.—Material facts concerning tuberculosis ...--.-.----------------------- The prevalence of tuberculosis. ..-----------------------+--++++--+------ Extent of the disease in the United States.........-..-.------------ Meat-inspection statistics. ..........--------------------------- Conditions shown by tests of herds ...-......--.---------------- Relations of contagion and environment to spread of the disease - - . - - MMbCECAlOsis inebritish berdga.25-- 3. see a ee etna Sonditlons onsthe continent OL HUnOpesessss oe ses = 2-2 ----42-—--- = TeNGcsestroll tUDELCULOSIS. ==. -.<-52- 22 ce osse esses es -2 ++ = 3--5-=- near aURerOltUllo CG WLOSIG= ae ae ae aera ee et arate lm I _ Effects upon the organs of the body -.---.-------------------------- Sy Lehn gies eta eo te ene ee ele ei ee ee Effects upon a herd of cattle ......--------+----.-----+------------- An experiment with tuberculous cattle. ....---.----- ts Se Sa Nh cnenWe toe iperculOsisa--a ss = os teak Sole ees eee sae ae Bees S} A TGEtMDeLelerDaAcllltis see ees Se ts eet ee See ne eels = Manner of infection and development of the disease -.....---------- mtectivenession milk or tuberculous COwWS--2--.-----2-------------- Mhetetiectiot insanitany Conditions C=. 3. 52. ==. -2--=- <2 - nase a----=- Mineraetectlon On tuerculOsisem= =< 2- so= Jee a= selec eee eee ee ~- Beam no my On WHE CMGNlos 455 caoosa ceases Cae aSeee Sone ooesees oes Immunization of cattle against tuberculosis .-.....---.----------------- arhyperemehMne Mts eae. see eae ee aoa ei Se re ne cin sean sin .,~ | Of tuber- City. | Year. | culous H City. | Year. | culous | swine. || swine. Berlimvxcs oc simian: ane cece 1895 -| 3.09 || Magdeburg ...... sete Sasa 1902 5.19 DOttiie-e28 eee eeesee ae 1899 | 45019 (SROtSGai ee sees tee ee 1900 TEb5) DOs secs oie Bee eck Jeet cee 1902 | O540) |e Zibtau Sees ee cee ey 1902 5.35 IDI OVAL eopetrsehaes Set a Retr eds Sate 1898 D26651| Zw Gat eet ete ene neers 1896 6. 06 1 DPae ahh eNE M n oc eene | 1902 | 57497 |aee On en ae Se eee 1899 3.89 Mar debutomssse sx cce te ees 1896 AE OTS eee Oi ee See. ee eee 1902 3.41 DO. sete Se ae a berate apo ere 1898 3. 55 It is plain that tuberculosis is far less frequent in the United States, with both cattle and hogs, than it is in Europe; but it also appears from the rate of increase shown by the statistics of various parts of the world, including our own meat-inspection reports, that unless its dis- semination is by some means checked it will require but a few years for it to gain the same headway here that it has acquired there. THE LOSSES FROM TUBERCULOSIS. It is a difficult matter to estimate with any approach to accuracy the losses from a disease like tuberculosis, concerning which the statistics are incomplete in every respect. There are now, however, approxi- mately 11,000 carcasses of beef and 65,000 carcasses of hogs condemned each year by the Federal meat inspectors on account of tuberculosis. We should not be far wrong in estimating the loss on these carcasses at present prices as $40 each on the beef and $12 each on the pork. MATERIAL FACTS CONCERNING TUBERCULOSIS. 15 We should therefore have as the net annual loss from the condemna- tion of carcasses $440,000 for beef and $780,000 for pork, or a total of $1,220,000. This statement, however, does not include the 647 parts of beef carcasses and the 142,105 parts of hog carcasses which it was necessary last year to condemn for the same cause, and the approxi- mate value of which can not be ascertained. In addition to the carcasses condemned by the Federal inspectors, there are a considerable number condemned by State and municipal inspectors. These are mostly carcasses of dairy cattle killed in the work of suppressing tuberculosis, or of cows no longer profitable in the dairy which are sent for slaughter to the smaller abattoirs. The ageregate number of these has not been ascertained, but in some years it has amounted to several thousand carcasses. The losses to the dairy industry from tuberculosis have been enor- mous from decrease in milk and depreciation and death of animals. The dairy herds have been affected toa greater extent than any others, and the infection has as a rule spread through the cows of a herd until 50 to 80 per cent of the animals were affected. In the early stages of the disease the product of the cows is not visibly lessened, but as the tubercular process develops the animals often become feverish, their milk is diminished in quantity, and they lose flesh and are no longer profitable. The losses from shrinkage of the milk and from the destruction of so many cows must be tremendous, but it has never been definitely determined. An extremely serious phase of this subject is the effect of the dis- sase in destroying valuable families of cattle and blood lines which can never be renewed. In most of the breeds there are certain families or strains of blood which have been developed by long and skillful selection and which represent the one marked success in a breeder’s life. The representative animals of such a strain are generally few in number and may all be in one herd. Under such circumstances the introduction of tuberculosis has often meant the annihilation of the strain and the blotting out of the achievements of a lifetime of toil and study. Such losses can scarcely be measured in dollars and cents, but they are no less real and no less serious as an obstacle to the development of the cattle industry. The losses to the breeders of purebred beef cattle have also been and still are so great as to merit the most serious consideration. When the individual animals of a herd are worth hundreds or even thousands of dollars, the introduction of a fatal infectious disease may soon cause the loss of a fortune, and this is just what has occurred upon many a breeding farm. Such a danger, always present and always menacing an industry, must discourage individual efforts and do much to prevent the attainment of lasting prosperity. The influence upon our export trade of regulations relative to 16 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. tuberculosis will probably become more and more unfavorable. Breeding and dairy cattle for Canada and Argentina must now be tested and found free from the disease before they will be admitted. The tendency everywhere is to make more stringent regulations, and any considerable increase in the prevalence of the disease would have an unfavorahle effect upon the sale of live animals, meats, and dairy products, even if burdensome regulations were not imposed. To meet successfully the increasing competition in the markets of the world it is important to have products which it can be shown are produced from healthy animals and which do not carry danger of any kind to the health of the consumer. THE NATURE OF TUBERCULOSIS. EFFECTS UPON THE ORGANS OF THE BODY. The most striking feature about the disease known as tuberculosis is the formation in different parts of the animal body, but particularly in the lymphatic glands, the lungs and liver, of small masses or nodules, yellowish, grayish, or whitish in color, which are called tubercles. It is from this characteristic that the disease receives its name. Tuber- culosis is therefore that diseased condition of the animal body in which tubercles are formed. There are, however, other diseased conditions accompanied by the formation of similar nodules which may also be called tubercles, and therefore it would be necessary in formulating an exact definition of tuberculosis to specify tubercles caused by the Bacillus tuberculosis. We might therefore say that tuberculosis is the disease caused by the Bacillus tuberculosis and characterized by the formation of tubercles in various parts of the animal body. It was formerly believed that the lungs were affected in nearly every case of tuberculosis, but more careful studies have shown that the glands of the neck and chest are even more frequently affected than the lungs. From the very careful autopsies made on the animals of the Soldiers’ Home, Washington, D. C., in 1893 by Dr. Theobald Smith,” at that time pathologist of the Bureau of Animal Industry, the following interesting information as to the parts affected was obtained: Total number ofanimals inthe herdeass. eee snes ee nee ee ee 60 Total number of‘animals infected (88 per cent)< 22-252 2222 eee eee 53 Number in which retropharyngeal glands only were affected --..........-.---- 5 Number in which the bronchial glands only were affected-.-.--.........--.--- 5 Number in which the mediastinal glands only were affected................--- 5 Number in which the thoracic glands but not the lungs were diseased.......--- 27 Numiber in«which lungs were atlected(S. = ae a= ee ee 20 Number withvexclusively thoraciellesionsm-- ease eee eee ee pene 26 Number with exclusively abdominal Jesionsssseeeceeee see ee eee eee i Total number in which retropharyngeal glands were affected_.........--..---- 9 Number in which disease of the thoracic organs was detected. .......---.------ 47 Number in which lungs were diseased and glands healthy .............---.--- 1 Number in which digestive tract, including head glands, was affected......-..- 26 Number in which intestinal walls were affected-................-----.------ eal Number in which mesenteric glands were affected .....----.---.2<------------ 164 Bulletin No, LUNGS OF A HEALTHY HOG, Bulletin No, 38, B. A. |. Plate Il, TUBERCULOUS LUNGS OF HOG ™ pees ra — Bulletin No. 38, B. A. |. Plate Ill, PORTIONS OF TUBERCULOUS LUNGS FROM CATTLE Bulletin No, 38, 8. A. I. Plate IV. TUBERCULOUS SPLEEN OF HOG. SPLEEN OF HEALTHY HOG. it MATERIAL FACTS CONCERNING TUBERCULOSIS. 17 Nimiber im: which portal glandsswere aftected < -:22/2 2. J. sos. ctl ene oc ceccees 10 Number in which mesenteric and not portal glands were affected .............- 10 Number in which portal and not mesenteric glands Were alteCteds sean. seco eo = 1 Number in which parenchyma of liver was riTun(Gl nf Cee od ee er 2 Number in which serous membranes were affected.......-------------.------- 2 Number in! whichvwudder glands were affected’.-....2-+--2------22-+---sce eens 1 From this statement the following table showing the location of the disease has been calculated in percentages: Organs affected. Per cent.) Organs affected. Per cent, Retropharyngeal glands only....-....-- 9.4 | Total digestive tract, including head Brouchialelands onlye-s-2s-eep.sceese 9.4 glandse S.sec sews oases ceo seesece 49.1 Mediastinal glands only ........-------- O4))|| atestinalawailllsti2enssstsecee ss taeceeee 9 Thoracic glands but not the lungs...... 50:9) Mesemtéricislandsesssacces su scesere see 30. 2 1 GD a a 27 | ee ee ee Oe ate Oe MME OLtal olan d seep ses sees teme eee seme oe 18.8 Lungs but not the thoracic glands Paes 1.9 | Mesenteric and not portal glands Serie: 18.8 Mhoracie organs Onlliyiesscsae. sesse es eseee 49.1 | Portal and not mesenteric glands...-..! To) Motalithoracic OreanSes ces. sc sees + oe 8827 || earenchym aot lnvenseacsssecesess ssc coe 3.8 Abdominal organs only.2-:=---2-------- 19h) /sSerousimemibrames}2ece aces sec ce- es eee 3.8 Total retropharyngeal glands. ........-.- L720) | iGlandsio@udGerkeeasce- och ace = sse es sae 1.9 This table shows the great frequency with which the tubercular lesions are found in the glands. If we add the cases in which the thoracic glands but not the lungs were affected (50.9 per cent) to those in which aie retropharyngeal glands only were affected (9.4 per cent), we find that 60 per cent of the cases had these glands, and not the lungs, affected. It is very seldom that the lungs are affected without the thoracic glands being also diseased. Doctor Pearson” has given the result of 1,200 post-mortem exami- nations made under his direction for the State live stock sanitary board of Pennsylvania. The following is a tabular statement of these observations, the organs mentioned being arranged in the order of frequency of infection. Practically all of the animals covered by this table were milch cows. Distribution of lesions in 1,200 cases of tuberculosis. Number | Per cent of cases | of cases ee eee in which | in which affected. | affected. Menras tina lekymp haticholandsta< saetercicco cc nccmacscciicace ce nccsc cs sone cence 725 | 60. 42 Rigitiinm es {So ssk seo ase cece Sa dsomnsteen. Uae hentai aden ceeacme ose is seeanieane nace 724 | 60. 33 UG eRe MMT TD a epancta waite ota ae ss sieete ial e’Siein wc etelalaieieioie ate's © Gleiaidisislelste sieremicieic si Shes bisoscaeaee see 685 | 57.08 IBrOMehTalulivmnp he tele ald See ere oe oe see ta lace cee ninatie oneaicceaicecetes 404 33. 67 Sura iisimbtestime season ono sice cae ese os ome aint enjoee oes buic soersGisns Jase ceneeis 388 32. 33 Mesenteric lymphatic glands. ... 278 23.17 TPG WOR CoouoesoonceobsGeosdoougaHe Sooe 264 | 22.00 [iy Oteemete etter sierra oe ecianicc icine Se stern es Cline aterioe tis oe nionie ao coerelaicicieee ceisler 247 20. 58 EAE Su CEStIM Cltiere eee ee oe Sia afue ecia a iemyaisyaios sectors Seine et cee ee emieee eileen 189 15.75 Postphanymrealslvamphatie slamdss <2 a. eee sneer eee ee pej niet Win oe ee 181 15. 08 RSTO MGW Sone page es orb anerOas soe ene eas oon soUaodUeGUdUaboDSaSoouE SoseoUuE 168 | 14.00 NN PYG CS IG SOM GOL arererarayoiectaaiiars onic cisleic incre oat ee are crowstn ec eras eletele Stretevereieier 161 | 3. 42 IDG ya NENeal oS oes oon rod eco aH eo poe sens Deeb DpoEst op Scone pe seed sabpeecoEescsoor 136 | 11.33 Rortalslymiplraticrmlanmdste sesctes 2 ac cca cisteite occ case's siocinis ecleeeeicisice oeeiicee ceo 123 10. 25 yp Metrere: anne Sto tena Keer ac nae wale iS aeae misevecie ieee ces sae ee ee eiyoaie ei aisc 108 9. 00 WGKIGI. oe eee obo 6 Ses ccatadcnoboL ECU E SBE Oo Oe Rane SOC aCOe Are no nooaSae Sousa er obooeaT 104 8.67 RET G ATG UTA pete are cere Teste cpa orc csi ss r= aicia eis ie. Sisal bie cleieisle sinc etelele se leicis cee ticle cisjaieinie 98 8.17 Lymphatie glands of shoulder 93 | 7.75 OM CM 69 a5q soshecgduonoosbocad GST bC CE MSE aEB ae beanpncgrsenoccopeoGcucresomscose 86 | Up Ald LG CL ere arctan ae ee a eee SC mIS Tana wimiaie nsw Sievers Soweigie ols ei Se wlaie oalee cletneeieiete 68 | 5. 67 OE ryt Seca te rte ae Pert te ie mee eens Cite nnials ocinc/cceleecden 66 5. 50 TSG Sl See sere eee peer Mie sce ete Se eee tg oo decid oo Stade see eee cig e lars actaserels 25 2.08 1881—No. 388—06 18 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. Of course in a great many of these cases lesions were found in a number of organs, and sometimes they were distributed throughout the abdominal and thoracic cavities. No reference is made to lesions in the brain, skin, muscles, bones, or joints, because these parts were not examined in all cases. Wherever the disease is located, it is usually made manifest by the formation of a number of tubercles the size of a pin head or smaller. If the tubercles are numerous and situated near to each other, they may become joined together in varying numbers, forming tubercular masses. Both the individual tubercles and the tubercular masses undergo certain changes by which they may become soft, cheesy, or semiliquid, and in other cases they may become gritty or hard through the depositing of lime salts. By such changes a lymphatic gland may be greatly enlarged and filled with tubercular material, which, when cut across, is found to be calcified and hard or broken down and soft- ened until it has acquired a cheesy or pasty consistency. The tubercles which form in the lungs go through changes similar to those just described as occurring in the glands, but, owing to the different structure of these organs, there are complicating changes in the lungs which give the lesions a somewhat different appearance. The irritation caused by the tubercles usually leads to the development of bronchitis with an abundant catarrhal secretion which fills the smaller air tubes, shuts off the air supply, causes the collapse of the lung tissue thus deprived of air, and leads to the depositing of yellow- ish cheesy matter in the air tubes and cells of this portion of the lung. This condition is known as tubercular broncho-pneumonia. In Plate I the lungs of a healthy hog are shown in order to enable the reader to compare these with the illustrations of tuberculous lungs. The color is uniform except for light and shade, the surface is smooth, and the tissue is spongy and elastic. The normal lungs of other kinds of animals have a similar appearance. The tuberculous lungs of a hog are represented in Plate II. Innumerable small tubercles are seen almost covering the surface, and many lobules are collapsed and of a deep red color. Toward the upper portion of the illustration, between the lunes, the enlarged and tuberculous bronchial glands may be dis- tinguished. These lungs were very severely affected, but the tubercles have for the most part remained isolated—that is, they have not united and formed the tubercular masses which are sometimes seen. Plate LI] shows different kinds of tubercular lesions observed in the lungs of cattle. In the lower figure there are small tubercular masses distributed throughout a limited portion of one of the lungs. The middle figure shows an aggregation or union of such masses, through which process a mass of considerable size has been formed, and around the border of this may be distinguished a white fibrous wall which when complete enveloped the tubercular material and shut it off from MATERIAL FAOTS CONCERNING TUBERCULOSIS. 19 the tissue of the lungs. The upper figure represents a tubercular mass similar to that just described, but older. The fibrous wall surrounding it is more distinct and thicker, while the contents are more broken down and homogeneous. When a large number of tubercles develop on the surface of the lungs, an inflammation of the pleura may be caused, with the forma- tion of much new tissue and the adhesion of the lungs to the ribs or the diaphragm. Sometimes the disease has a peculiar tendency to the development of tubercular growth upon the pleura and other serous membranes. The tubercular masses bud and branch, thus forming large wartlike growths; or groups of nodules may even hang from the surface suspended by delicate threads or fibers giving the appearance of a bunch of grapes. These collections of tubercles have often been called grapes, and this form of the disease is known as ** pearly dis- ease,” on account of the pearly color and glistening appearance of the serous membrane covering the projecting buds and spherical masses. In many eases both the lungs and serous membranes are affected, but often there are extensive growths of this kind upon the surface of the lung, while, singularly enough, the tissue of the lung remains unattacked. With extensive tubercular disease of the lungs and pleura the bronchial and mediastinal kymphatic glands generally become loaded with tubercular deposit and enormously enlarged. In some instances they constitute masses of tubercular material many pounds in weight. The organs in the abdominal cavity are also frequently the seat of tubercular disease. In the herd of the Soldiers’ Home, above referred to, more than 40 per cent of the animals had abdominal lesions. The mesenteric and portal glands are the organs most commonly affected, but tubercles are often found in other lymphatic glands of this region, and also in the liver, spleen, kidneys, ovaries, uterus, and even in the intestinal walls. . In Plate IV the figure to the right illustrates the appearance of the normal spleen of a hog. Its uniform color and regular outline should be noted. The figure to the left represents the tubercular spleen of a hog. Observe here the yellowish masses of tubercular material which cause elevations of the surface, and the color of which may be plainly distinguished through the membrane which covers the organ. Plate V was made from a case of tuberculosis of the liver of a cow. A large portion of the lobe of the liver which is shown in the plate has undergone tuberculous changes and been converted into a solid mass of tubercular material. The nodules seen in this illustration are in various stagesof the disease, but the majority contain the yellowish, partly cheesy, partly gritty substance which is characteristic of advanced tuberculous degeneration. Plate VI is an illustration made from a case of severe tuberculous 20 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. pericarditis of a cow. The pericardium or sac surrounding the heart is seen greatly thickened by the formation of tubercular material, and the heart itself is compressed and misshapen. In Plate VII the lower figure represents the tuberculous ovaries of a cow. Many nodules of a size approximating that of a pin head are visible over the surface of the organ, and some are deeply buried in its substance. The upper figure was drawn from a portion of a child’s intestine which was thickly covered with small tubercles. The great development of the tubercular process in this case is readily appre- ciated from the appearance of the plate. This class of cases has been attributed to infection taken into the stomach, and some of these cases are supposed to be due to infected cow’s milk. e The udder of cows is sometimes attacked by tuberculosis, in which case one of the quarters is found to be swollen, uniformly firm or hard, and painless. In rare cases one-half of the udder may be affected. Tubercles are formed throughout the affected part of the organ, and there may be tubercles and tuberculous ulcerations upon the surface of the membranes lining the milk tubes. When such a condi- tion is established the milk becomes thin and watery and contains innu- merable tubercle bacilli. As the disease progresses larger nodules, such as have been described in other organs, form within the udder and undergo degeneration, softening, and liquefaction. If such a tuberculous mass opens into a milk duct, as is often the case, the liquid or semiliquid contents become mixed with the milk. Plate VIIT isan illustration of a tuberculous udder which has been cut across to show the distribution of the tuberculous material. This part of the organ is filled and distended with the tuberculous deposits, and the milk cistern showing near the lower portion is ulcerated, lined with tubercles, and covered with cheesy particles. At the upper portion of the illustration may be seen the supramammary lymphatic gland, which is greatly enlarged and studded with small tubercles. Tubercles are often found in the lymphatic glands in front of the shoulder and in the flank, and in, those embedded in various parts of the muscular tissue. As such glands are situated in the portions of the carcass used for food, it is important that they should be examined before the carcass of a tuberculous animal is utilized for this purpose. A tuberculous lymph gland is shown in Plate LX. The bones may also be invaded by the tubercular process, especially in swine, and sometimes the whole interior of one or more bones will _be filled with tubercular material, either just developed or undergoing degeneration. Often the joints are affected, causing swelling, inflam- mation, and lameness. The brain and spinal cord are by no means exempt from tuberculous disease, but owing to the difficulty of remoy- ing these organs for examination we have fewer statistics relative to them than to most other parts of the body. Semmer found tubercu- Bulletin No, 38, B. A. | Plate V TUBERCULOUS LIVER OF COW. i a ' . + ' i = ie ¢ | . + H i @ « ~ it i - Bulletin No, 38, B. A. 1. Plate TUBERCULOUS PERICARDITIS OF COW. Vi. : yoo uae ies a 7 = a ? Bulletin No, 38, B. A. |. Plate VII, TUBERCULOUS INTESTINE OF A CHILD. TUBERCULOUS OVARY OF COW. | = } ; t ® : | . 7 2 : Bulletin No, 38, B. A. |. Plate VIII, TUBERCULOUS UDDER OF COW. va Bulletin No. 38, B. A. |. Plate IX. Haines del. roo4. ALHOEN & CO. BALTIMORE TUBERCULOUS LYMPHATIC GLAND OF COW. MATERIAL FACTS CONCERNING TUBERCULOSIS. DT: losis of the brain in + out of 40 cases examined. The tubercles are located on the membranes of the brain and spinal cord, and are also found scattered through the interior tissue of these organs. It will be seen from what has preceded that tuberculous disease may be found in any part of the animal body, and that while there are certain organs which are affected more frequently than others, none of the living tissues is altogether exempt from its invasion. The generalized form of tuberculosis is that in which the infection gets into the blood and is distributed through the circulation to many parts of the body. Slaughterhouse statistics of different countries of Europe indicate that about 9 or 10 per cent of the cases of tubercu- losis in cattle are in this form. Rieck, quoted by Ostertag, states, as a result of the careful examination of 430 cases of generalized tuber- culosis in the abattoirs of Leipzig from 1880 to 1891, that the follow- ing percentages indicate the proportion of these cases in which the different organs of the carcasses were affected: Organs. | Percent. | Organs. Per cent. = ees — ee ees | Se Se ee a | = NG UTNY PS Rieyepes veneer (a aioe sere ee eee A 100.0 | Muscles and intermuseular lymph | ILAWGR a8 GRR ASear neon aoe Beano Een 83.0. | POTS Soe ees ee een ae ae ee: 49.3 MES TR Cam al Re see as ee ae a aS aa WS503 || SPlCCN Sean cjeccm cee ee eee eee aes 18.6 NELOUSs EMD TAU CS hee soe ese ene Opa UGC Clan scstine: scoccmsece ee Nee eee 16.7 IkatGhVeENE Soe ccacuodenee. Sods ceeecse tees D230 |p OWES! Sots sleet ict memantine Seer we 8.8 SYMPTOMS. In the great majority of cases of tuberculosis in animals the symp- toms are slight and not at all clear in their indications. As the func- tions of the body must be disturbed more or less before any symptoms are apparent, it is plain that in the earliest stages of the disease there are no symptoms, and that when symptoms develop the disease is already considerably advanced. It is only when the affected part is located where it may be easily examined that symptoms are shown by which the infection may be detected at a comparatively early stage. Thus when the udder or the glands of the neck are the seat of tuber- culosis the existence of the trouble is more likely to be revealed than when the affected organ is within one of the body cavities. If the larynx, the air tubes, or the lungs are affected there is a short cough, which is heard particularly in the morning at feeding time or when the animal is let out of the stable in the cold air, or after it has been drinking cold water, and especially after violent exertion. This cough generally becomes more prolonged and convulsive as the disease advances. In case the uterus or ovaries are effected there may be abortion or sterility with abnormal sexual manifestations. If the intestines are affected there may be irregular attacks of diarrhea. If a joint is dis- eased it is revealed by lameness. As the disease progresses the general health of the animal and the 22 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. functions of nutrition are affected. Animals which have been in good flesh and laying on fat fail to profit by their food and begin to lose flesh; there is a lusterless, staring, rough coat of hair, the skin becomes tense, the bones prominent, and the eyes sunken in their sockets. The milk secretion diminishes and the milk becomes thin, watery, and blue. In case the serous membranes of the chest become irritated by the tubercular deposits, pressure applied over the ribs may cause the diseased animal to cough, moan, seek to escape, and otherwise manifest evidence of tenderness in this region. The ear applied to the walls of the chest may sometimes detect abnormal sounds, such as loud crepitation, gurgling, whistling, and creaking, or there may be areas where the respiratory murmur is entirely lost. Percussion sometimes shows abnormal resonance and sometimes areas of dullness corresponding to tubercular deposits or adhesions of the lungs to the chest wall. In most animals there is high temperature, progressive emaciation, and loss of strength until death results. With some cases the general nutrition of the body remains unaffected and these symptoms of the final stages of the disease are postponed until after the lungs or other vital organs have been almost completely filled with tubercular deposit. But if the disease continues to make progress there must come a time when the nutrition and vigor fail to maintain themselves and rapid prostration follows. There are cases, however, with animals as with men, in which the forces of the body triumph over the disease, and the progress of the tubercular formation is arrested. The tubercular material is then inclosed by fibrous walls which shut it off from the living tissues of the body, caseation and softening or calcification take place, and in the course of time the bacilli may die and disap- pear. Unfortunately, these cases are the exception and not the rule. In those cases which progress to a fatal end the attitude and general appearance of cattle are quite characteristic during the final stages. The emaciation is extreme; the outlines of the bones are clearly visi- ble; the skin is tightly drawn over the skeleton; the coat is rough and without luster; the animal remains almost constantly standing; the nose is raised and the head extended on a line with the neck; the elbows are turned out to facilitate the expansion of the chest; the eyes are sunken, and there is a haggard expression to the face in harmony with the general appearance of the body. The symptoms of tuberculosis in hogs are very obscure and difficult to detect. In the great majority of cases no symptoms are noticed and the disease is only recognized by an examination of the carcass. The parts most frequently affected are the glands of the neck, the bronchial, mediastinal, mesenteric, and portal glands, the fiver, lungs, kidneys, and spleen. In numerous cases the glands of the carcass are affected, and tuberculosis of the bones and joints is common. MATERIAL FACTS CONCERNING TUBERCULOSIS. 93 Although there is a great tendency for tuberculosis to spread to different parts of the body in swine, causing it to become more fre- quently generalized with these animals than with cattle, the rapidity with which they take on fat apparently enables them to resist the destructive influence of the disease, at least to the age at which they: are generally slaughtered. Animals which come to market fat and appear perfectly well just before slaughter may be found quite seriously diseased. In some cases, however, swine may show enlargement of the glands of the neck and of other parts of the body, diarrhea, emaciation, and tubercular inflammation and swelling of one or more joints. When the nutrition of the body is affected, as shown by loss of flesh, the disease usually runs a rapid course and causes the death of the animal in a few weeks. EFFECTS UPON A HERD OF CATTLE. It is no less important to study the effects of tuberculosis upon a herd of cattle than to study its effect upon the individual animal. The experience of those who have had herds free from the disease but who have had the misfortune to introduce it and have seen it develop among their animals must be of the greatest value to others who desire to guard against it. A number of such cases have been carefully studied at the experiment stations and elsewhere and the principal features of the outbreaks ascertained. AN EXPERIMENT WITH TUBERCULOUS CATTLE. Phelps” relates experiments with four condemned cows which were placed by the Connecticut State cattle commission at the disposal of the Storrs Experiment Station for the purpose of making some obser- rations and experiments on bovine tuberculosis. The herd from which these animals came had been officially tested in March, 1896, and several animals in the herd were condemned and slaughtered, although the four cows mentioned failed to respond and were tagged as free from the disease. In October, 1896, the herd was tested again by the commissioners, and these four cows responded and were then condemned as tuberculous. Shortly afterwards they were brought to the station and were kept in quarantine until they were slaughtered in the fall of 1900. These particular animals were chosen for the experiment because there was good reason to believe that the disease was present in its earlier stages. While the cows were at the station they were kept isolated from other cattle in a high, light, and airy stable with about 1,500 cubic feet of air space per cow, although later several calves which were used in the experiments with the cows occupied the same stable. Adjoining the stable was a small yard about one-half acre in area in which the animals were allowed to exercise several hours each 24 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. day, except in very stormy or extremely cold weather. No special treatment for the disease was attempted, but good care and feed were afforded at all times. During the first year that the animals were under observation all four cows remained in good condition and showed no outward sign of disease. It is evident that these cows were received at the station soon after their infection, when the disease had made but slight progress and before the general health of the animals was noticeably affected. They were kept under excellent sanitary condi- tions, with outdoor exercise and good food, and were protected from the worst weather. They should, therefore, have done much better than the average farm cow after it is infected with this disease. The history of these cows at the station is very instructive, and is. in brief, as follows: Cow No. 1537. This cow produced a vigorous calf April 5, 1897. The calf suckled its dam for six months, and was then placed in the college herd. During 1898 the cow appeared to be in vigorous health and remained in good condition of flesh. She dropped a well-dev eloped calf in September, 1898, w hich was allowed to suckle its dam for about a year. During 1899 she remained ina y igorous state of health, and produced a healthy calf in December, 1899. Although this calf appeared vigorous and strong at birth, it was soon after attacked by scours and died in a few. days. During 1900 the cow remained in good flesh, had a sleek coat, and continued to give a good flow of milk. Early in the year she "devel yped a slight cough, but otherwise appeared i in perfect health when killed in November, 1900. Examination of the car- cass showed the mediastinal lymphatics to be tube sreulous, and a tuberculous nodule was found in the right lung. The other organs were normal. Cow No. 1341. This cow ‘dropped a dead calf in March, 1897, the carcass of which was carefully examined, but revealed no signs of tuberculosis. She produced a well- developed calf in August, 1898, and seemed to be ina good state of health through- out the following w inter, During 1899 she remained in fair flesh and gave a good flow of milk until July. At that time, while being fed green oats and peas, she was attacked by scours and began to run ‘down rapidly. She ceased giving milk fora short time, but when plac ed on dry feed began to regain flesh and “mnilk flow. She remained in a fair state of health during the. fall, but had a tendency to looseness of the bowels. A healthy calf was produced in February, 1900, which was followed by a good flow of milk for several months, but during the spring and summer she lost flesh rapidly until her flanks were hollow and her ribs protruded plainly. The coat became rough, the eyes dull and sunken, the cough increased, and the breathing became more frequent. This cow continued to scour intermitte ntly, and when killed in November, 1900, was generally emaciated, although continuing to give milk up to the time of her slaughter. Two-thirds of the right jung and one-half of the left lung were filled with tuberculous tissues and the mediastinal lymphatics were diseased. Cow No. 1343. This animal became quite fat during the early part of 1898. She dropped a rather small calf in August, 1898, and was considerably thinner than usual for three months after calving, but scon after that began to gain in flesh. Later in the fall it was noticed that she had a persistent cough. During the spring and sum- mer of 1899 she continued to give a fair flow of milk, but was not as fat as in 1898, Her cough increased during the winter of 1898- 99, and in the followi ing spring it was noticed that she coughed badly after eating dry feed or when made to exercise vig- orously. Howeyer, she produced a vigorous calf in December, 1899, but this was soon after attacked by a mild form of scours, from which it recovered. She gave a fair flow of milk during the early part of the year 1900, although she was losing flesh and had an increasing “cough and short, hurried breathing. During the fall of 1900 she lost flesh rapidly, “had a rough coat, "sunken eyes, and ‘protruding ribs. She lost her appetite, and in October ceased to give milk, and when slaughtered in November was very much emaciated. Up tow ithin a year of the time of slaughtering, this cow had been the fattest and sleekest of the four. The examination of the carcass showed both lungs badly diseased, almost solidified with tuberculous tissue, the chest walls covered with tubercles, and the mediastinal and mesenteric lymphatics badly tuber- culous. Tubercles were found on the rumen and the diaphragm. Cow No. 1344. This cow remained farrow during 1898, but continued to give a good flow of milk. During the fall of 1898 she gained in flesh and appeared to be in MATERIAL FACTS CONCERNING TUBERCULOSIS. 25 a healthy and vigorous condition. She remained in this condition until some time in the summer of 1899, when she showed lameness in the right stifle joint. She calved in October, 1899, but the calf was weak at birth, and refused to eat. It died about a week after birth. The cow gave a good flow of milk for several months after calving, but was thinner than usual. During the early part of 1900 she lost. flesh rapidly, though still giving a good flow of milk. She also developed a severe cough, which was especially noticeable when she was made to exercise vigorously. The lameness in the stifle joint increased in severity and became very troublesome to the cow. She lost flesh during the summer and fall, and, although not as emaciated as Nos. 1341 and 1342, was quite thin, hada rough coat, and appeared to be in a bad physical condition when slaughtered in November, 1900. The examination of the carcass showed the mediastinal lymphatics diseased and an abscess in the left lung. With three of the four cows in this experiment the disease pro- gressed from the very earliest stage to a point where the animals were worthless within about four years. With the fourth animal it remained nearly stationary and did not apparently affect the general health. SPREAD OF TUBERCULOSIS BY DISPERSION SALE. Russell” gives the following example of the dissemination of a dis- eased herd: In October, 1908, a public sale was held in one of the southern counties of Wiscon- sin, at which a herd of 46 head of cattle were disposed of in order to divide up the interest of the landlord and the tenant. These 46 head were purchased by twelve persons. The landlord, wishing to retain what he thought were the most valuable animals, had a friend buy in for him 18 head, while the tenant bought 3 for himself. One of the parties who had purchased 6 of these animals decided in the following February to have his herd tested for tuberculosis. A neighbor, hearing that the test was to be applied, asked to have his family cow tested at the same time. The result of the test was to show positive reactions in the case of this single animal and also in 3 out of the lot of 6 which had been purchased. This revelation led the original owner to inyestigate the condition of the portion of the herd which he had pur- chased, and in this case 14 of the original 18 were found to be affected. The matter at this stage was brought to the attention of the State live stock sani- tary board, and after a lapse of some weeks, so as to secure normal results, retests of these herds were made. In addition, all the herds were tested into which any animal had been introduced from the herd dispersed at the sale. The results of these tests are shown in the following table: Dissemination of tuberculosis into various herds by sale of stock. = -| Number of | » -| Number of Fe Nunber of) “gnimals. | Number of) reactions nerd from origi- reactions, |i animals : | nal herd, | ~* | purchased. | | { Peer eee ee eae eles ae Se ee os es meeceioe ces PAL 5 3 3 G) 5 AEE Si Ra ae Seer gh ea we AE a ee 18 | 18 | 14 | 14 eS ae ee TSC a Pne eae ratatsinicie efoteicrolere eit iote cinisetert Remon ere 38 6 3 | 3 Aaa eels amre ia eisic one le ia Pane Se eeleie nie eo elnajnioe ee te 8 | 3 | 4 2 Beene Varied Cote a Pere US bel eC ele ted ot 5 | 2 | 2 1 (ES ne co uione Caer Base See ete aE nee ie rk 3 | 3 | 3 | 3 Ree arate itt ate Seiarerae cine sche tecciseescactweneeanes 1 1 1 1 Sh crs oi tae ce Ras a a Sen SR 15 | 1 | 1 | 1 Pe ate ear ere ear ietatee i eine Skis Cais c atem ios Gace Gee oE 32 | i 1 1 Oe aes aoterciiea oe serena comes deed goe su sces ees 18 | 3 0 0 1 ele BCS EE Gres Ge gee ioe SOE eae a eee eae 2 | al 1 1 HN Das are reteie sate ae nie see iae on one oe Noes Same Ese ee omens 2 | Zh 2 2 ee eee eee ee ae ne ee ee Sa is ES oo 22 | 9 | 1 i It is evident from the above data that the originally affected herd was badly diseased, as 33 out of the total number of 55 disposed of at the sale or before responded to the tuberculin test. And yet none of these animals showed any appearance of the disease, and no one ques- tioned their healthy condition at the time of purchase. The fact that 26 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. the owners bought in a large portion of the herd is evidence that they had no idea of the existence of this serious disease. It was exceedingly fortunate that the first test happened to be made so soon after the sale of this herd, as the disease had apparently just begun to spread in the herds to which the animals from it were taken. It is, nevertheless, a good example of the extent to which the infection may be disseminated by the sale of animals from a single herd which is apparently in healthy condition. HISTORIES OF AFFECTED HERDS. The following history of the introduction and development of the disease in the herd of the Connecticut Agricultural College is a strik- ing example of the danger of purchasing cows so long as tuberculosis is prevalent in dairy herds: * Previous to 1896 the herd consisted of grade animals, mostly of Jersey and Guernsey blood, but in that year 15 registered Jerseys, Guernseys, and Ayrshires were pur- chased. Since then the acquisitions to the herd have been from the natural increase of these animals, and the occasional purchase of grade cows. The herd was exam- ined by the veterinarian and tested with tuberculin in 1896. The registered animals purchased during the year were also tested, and the herd was pronounced free from tuberculosis. The tuberculin test was applied again in 1897, with no reactions. In October, 1897, several grade cows were purchased, including ‘‘ Fannie,’’ a grade Guernsey. This cow was bought of a neighboring farmer, who had owned and raised her from a calf. Her owner reports that he had never had tuberculosis in his herd and had never used the tuberculin test. Fannie was a smooth, plump cow, and apparently in perfect health. When purchased she was tested with tuberculin, and, as she did not respond, was given a permanent place in the herd. She remained apparently in good health until about November 1, 1898, when she began to refuse a portion of her allowance of silage, and soon after commenced to scour, but at no time did she cough. From this time on she ran down rapidly, and was killed on November 20, as it was evident that she could live but a day or two longer. A post- mortem examination showed a generalized and advanced case of tuberculosis. The herd was tested with tuberculin December 28, 1898, when 12 animals responded; it was again tested May 22, 1899, when 3 more responded; it was tested for the third time December 7, 1899, when 2 more responded; and it was tested for the fourth time April 16, 1900, when 1 additional animal responded. No further reactions occurred in subsequent tests, the last of which recorded was made on February 17, 1902. Including the original tuberculous animal, there were, consequently, 19 diseased animals found in this heard of 49 animals, the disease having spread to that extent in about two and one-half years, notwithstanding that it was discovered at the end of the first year, and that affected animals were removed as fast as they were revealed by the tuberculin test. Russell* gives the following history of an extensive outbreak of tuberculosis among cattle which recently came to light in the herd of a prominent dairyman supplying milk to the city of Beloit, Wis.: The owner had a fine dairy farm on the outskirts of the city, and had constructed ample stable room to accommodate his herd. The business had developed until at the time of examination 70 animals were kept, 46 of which were in milk. A veter- inary examination of an animal somewhat out of condition revealed the presence of tuberculosis, much to the surprise of the owner, and the tuberculin test was then applied to the whole herd. Fifty-seven in this herd of 70 reacted to the test. Those that escaped were for the most part young stock. Thirty-three of the best conditioned of the 57 reacting ani- mals were shipped to abattoirs for immediate slaughter, and of this number only 18 passed Federal inspection. Of the 24 killed on the farm not to exceed 7 would have passed for beef had they been sent for slaughter. Thus it appears that 32 of the 57 that reacted were so badly affected as to require total condemnation of the carcasses. lod ( MATERIAL FACTS CONCERNING TUBERCULOSIS. 2 The owner was in California, buf it was admitted by the herdsman who had handled the herd in previous years that a considerable number of animals had died or been killed from year to year as long ago as 1897. Frequently animals had been shot to get rid of them as they pined away. No examination was made and the matter was allowed to drift on until the startling revelation was made by the use of the tuberculin test. The slaughter of this herd revealed many cases of advanced tuberculosis, and in some instances even the udders were found diseased. The farm had well-constructed barns and stables, which were kept in a clean and sanitary manner, but no provision was made for ventilation. Within a week from the time this first-mentioned herd was disposed of, another was examined in the southern part of the State in which even a worse condition was found. In this instance the herd consisted of 72 animals, many of which were fresh in milk, as the product was to supply a Swiss-cheese factory. The condition of the stock revealed by the tuberculin test was shocking. Of the 72 animals tested, 69 reacted. Only 1 mature animal, a yearling bull, and a young calf escaped the disease, This widespread distribution of the disease was found to be due to the usual cause, neglect and failure to provide proper sanitary surroundings. For several years the owner had been losing animals from time to time, but made no effort to learn the cause of the trouble. “This last winter 5 died, the year before 2 others, and during previous years still others. Four years ago he sold to a neighbor 5 head of young stock, which were kept on pasture during the summer. In the fall they w éighed less than when bought, and were condemned when shipped to Chicago. Later 7 or 8 others were bought for shipment, 3 of which were condemned when inspected. The post-mortem findings in this herd revealed many cases of generalized tuber- culosis, some of which were in a most aggravated form. Ina number of cases the udders showed well-marked physical signs of disease. The development of the dis- ease in young stock in both lung and body cavities, with the infection of the bowel itself, bespoke a double infection, through the milk as well as through the air. The stable in which this entire herd of 70 head was kept, with about a dozen young calves, was located in a stone basement, in which there was absolutely no provision for ventilation. A little light filtered in through five or six tightly closed sash win- dows of three 8 by 10 inch panes of glass to each window. The interior of the stable was so dark that one could scarcely see to read ordinary newspaper print unless the doors were left open. In addition to these general insanitary surroundings, the manure on the floor of the stable was over a foot thick. The way these two herds were handled is markedly contrasted with the course of action that was pursued in the following case: A few weeks ago a member of the farmers’ course at the Agricultural College wit- nessed a demonstration of the tuberculin test, and while he had no reason to suspect the presence of the disease in his own herd, he went home with the thought that it would be prudent for him to apply the test and satisfy himself as to the actual con- dition of his animals. In his herd of 25 only 1 was found affected, and this was a registered cow that had been bought a few months before for the sum of $150. This animal was the only recent purchase that had been made. Recently another _correspondent wrote that he applied the test to his herd, and found that 3 out of 5 registered Holsteins that he had purchased a short time before at an expense of $1,500 were affected. THE CAUSE OF TUBERCULOSIS. THE TUBERCLE BACILLUS. Tuberculosis is caused by a bacterial organism knownas the Bac7//us tuberculosis microbe, which, so far as is known, does not multiply out- side of the animal body except under the artificial conditions supplied in laboratories. As we find the bacillus in the body of an animal it is very exacting in the conditions which it requires for its growth, and for a long time bacteriologists found it difficult to make it develop in their laboratory cultures. Careful study of its peculiarities has, how- ever, resulted in the discovery of methods by which it is now easily isolated from the tissues of the affected animals and grown in pure cultures. The longer it is grown in the laboratory the more readily 28 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. it is cultivated, as it adapts itself gradually to the new conditions; but in acquiring this exalted power to live and multiply outside of the animal body it generally loses some of its disease-producing power and becomes less and less virulent until in the course of time it may not be able to cause disease in the most susceptible animals. The tubercle bacillus produces tuberculosis in all species of domesti- cated animals and probably in most species of wild animals, though some species of animals are very much more susceptible to its effects than others. It is able to multiply in the bodies of birds whose tem- perature is considerably higher than that of mammals, and it is like- wise able to multiply in the bodies of cold-blooded animals whose temperature is far below that of mammals. It therefore lives, propa- gates itself, and causes disease under a great variety of conditions—a variety which is truly surprising when we consider the delicacy of the germ and tbe difficulties which were encountered in cultivating it in the laboratory. The tubercle bacillus as it is found in widely different species of animals is not always identical in its characteristics, although there are certain general features which it always retains. Its peculiarities in regard to staining are the most striking of these. It does not take up the usual stains which are successful with other bacterial organisms, and consequently must be stained by special methods. Koch first sue- ceeded in coloring it by leaving it for several hours in a solution of methylene blue, to which caustic potash had been added; but this method was soon superseded by a solution of gentian violet in water saturated with anilin oil, which was introduced by Ehrlich. Of late years carbol-fuchsin has been quite generally adopted for this purpose. Another peculiarity of the tubercle bacillus is that having once taken a stain, it fixes it very firmly, and it is, therefore, much more difficult to decolorize than other bacilli. The dilute mineral acids will remove these colors from animal substances and from other bacteria, but not from the tubercle bacilli. Advantage is taken of these peculiarities to make microscopic preparations in which the tubercle bacilli appear brightly stained while everything else is free from color, or to make these preparations so that the tubercle bacilli will appear red and all other micro-organisms will be blue. The tubercle bacillus obtained from human beings is able to grow between the temperature limits of 80° and 40° C.; that obtained from birds is able. to grow between the limits of 25° and 45° C.; while a stock of tubercle bacilli obtained by Friedmann from a tuberculous turtle was able to multiply at the freezing point and its temperature limits were placed by the discoverer at 0° to 48° C. The bacilli from these different sources have different habits of growth in cultures, and some under the microscope appear longer, thinner, and more beaded than others. There is also a great difference in the virulence cf the MATERIAL FACTS CONCERNING TUBERCULOSIS. 29 various stocks for different species of animals. Human bacilli are only with difficulty made to produce disease in fowls or in cold-blooded ani- mals, and the greater number of such stocks have little or no effect upon bovine animals. Various investigators have succeeded, however, in mod- ifving the different stocks of bacilli, and have been able to infect success- fully birds and cold-blooded animals with human and bovine bacilli, and have also infected mammals with the tubercle bacilli of birds. It appears, therefore, that the tuberculosis bacillus is one which is able to adapt itself to a wide range of conditions, and that the bacillus as found in the tuberculous lesions of birds, mammals, and cold-blooded animals is the same organism but modified somewhat by the conditions of environment. MANNER OF INFECTION AND DEVELOPMENT OF THE DISEASE. The tubercle bacillus may enter the body through a number of chan- nels and thus cause infection. With cattle it is most frequently drawn into the air tubes in the form of dust floating in the atmosphere of the stable. In many cases, however, it enters into the alimentary canal with food that has been soiled with the saliva or other secretions of diseased animals. It may also gain entrance through a milk duct or through the vaginal opening, or by means of a wound. The bacillus uppears to be able to penetrate the mucous membranes, at least in cer- tain places, even when there is no wound or abrasion, and it may pass through the membrane without leaving any tubercular material or other sign to show where it gained entrance. However, in its progress through the tissues it is usually soon arrested either by a lymphatic gland or in some other manner, and then it multiplies and causes the formation of a tubercle. The channel by which the infection occurred may generally be determined with some degree of certainty by the location of the older tubercles. If the bronchial or mediastinal glands show the earliest lesions the infection probably came through the in- spired air; but if the retropharyngeal, mesenteric, or portal glands have the oldest lesions the infection was probably through contami- nated food. ; When the tubercle bacilli have lodged in or invaded any organ their irritating effect upon the tissue surrounding them sets up changes similar to those seen in ordinary inflammation. The fixed connective tissue cells and the cells of the endothelium of the capillaries begin to multiply and produce large numbers of new cells which group them- selves side by side in the form of a hollow sphere around the bacilli. These cells are then called epithelioid cells, and for the reason that it is composed of such elements the tubercle at this early stage is known as the epithelioid tubercle. After the tubercle has made some progress in its development by the process just described and has become barely visible to the naked 30 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. eye, small round cells, called by some lymphoid cells, begin to gather around the sphere of epithelioid cells and may become so numerous as to obscure the latter and cause their disappearance. ‘These round cells undoubtedly come from the blood vessels in the vicinity which have been affected by the adjacent tuberculous growth. When these lym- phoid cells have increased in number until they predominate in the newly formed tubercle, this is called a lymphoid tubercle. When the tubercie develops to about the size of a pin head, the lymphoid cells have usually become so numerous that they interfere with the nutrition of the central portion, and, therefore, the cells located at the center begin to die. As the cells die they disintegrate, and there is formed a granular, caseous material from which the bacilli have disappeared. When this process occurs slowly it is accompanied by the formation of giant cells, thac is, large cells containing numer- ous nuclei. These cells are formed either by the fusion of a number of cells together or by an abnormal increase in the protoplasm of a single cell together with the multiplication of its nuclei. As the tubercles increase in size, either by the addition of more cells or by the fusion of two or more small tubercles, the necrosed and caseated portion at the center becomes larger, and as this process con- tinues tubercular masses of considerable size may be formed, having the same general appearance as the smaller tubercles, but with a rela- tively larger proportion of caseous material. When the center has undergone partial caseation, the epithelioid cells surrounding the tubercle may be gradually changed to connective tissue cells, which are deposited in successive layers and thus form a fibrous wall. By the time the former cellular elements of the tubercle have disappeared this fibrous wall or capsule becomes firm and resist- ant and completely isolates the necrotic focus. The caseous material within the tubercular mass may soften and form a liquid resembling pus, or there may be a deposition of caleare- ous salts which at first form as small angular granules and later co- alesce into larger nodules until finally the entire caseous material may be calcified. This change is very common with both cattle and hogs. After an animal has been infected with tubercle bacilli and the first tubercle has commenced to develop in the manner above described, more or less bacilli may be carried from this first point of infection with the streams of lymph or blood and lodge elsewhere to cause the formation of other tubercles. When the bacilli are carried through the lymph channels they usually are deposited before going any great distance, and hence, in this case, the tubercles are limited to one organ or to one part of the body; but if the bacilli penetrate the blood ves- sels in great numbers, as sometimes occurs, they are carried to all parts of the body and generalized tuberculosis is the result. The ways in which tubercle bacilli escape from the body are quite as — MATERIAL FACTS CONCERNING TUBERCULOSIS. 81 interesting from a practical point of view as the ways in which they enter it. There are a number of channels through which they may be disseminated, but the most common ones are the air tubes, the digestive tube, and the milk ducts. Tubercles which develop near these channels, or in the mucous membrane lining them, may soften and discharge their contents into the tubes. In the case of the air tubes the material is coughed up, contaminates the saliva, and is partly distributed in the mangers and racks, and over the litter, and partly swallowed to pass away with the excrement. In the case of tubercu- lar ulcers on the internal surface of the intestine, or of cavities in the lung opening into the bronchi, or of similar lesions communicating with the milk ducts, there may be a continuous development of the bacilli and an equally continuous discharge of vast numbers of these germs into the intestine, the bronchi, or the milk ducts, as the case may be. An animal so affected is most dangerous and may soon infect most of the individuals in the herd. The bacilli are less frequently distributed from the genito-urinary organs, although such distribution may occur when the kidneys or uterus are the seat of the disease. On the other hand, the tubercular lesions may be so situated that they are closed in and have no channels of communication with the exterior, as in those cases where they are confined to a bronchial, mediastinal, or mesenteric lymphatic gland. Under such conditions an affected animal may remain in a herd for a long time without com- municating the disease to the other animals of the herd. But prob- ably in the majority of such cases there will sooner or later be an extension of the tubercular formation in the affected animal, when it may suddenly and without warning begin distributing the bacilli and infect the animals which are stabled or pastured with it. This explains why in some instances a tuberculous cow may infect the greater part of a large herd within a few months, while in other instances such a cow may remain in a herd for several years and no other animals become infected. The disease is of the same nature in both cases, but in one case the bacilli are able to escape from the body of the diseased animal, while in the other they are imprisoned and unable to do further harm. INFECTIVENESS OF MILK OF TUBERCULOUS COWS. The milk of tuberculous cows is a very common medium for carry- ing the tubercle bacillus to other animals, for while every cow affected with the disease does not secrete milk contaminated with the bacillus, there are frequently one or more cows in an infected herd whose milk is infected, and this, in turn, infects all milk with which it is mixed. There has been a great difference of opinion as to the proportion of affected cattle which yield milk containing the tubercle bacilli. Some have held that the udder must necessarily be diseased before the bacilli can find their way into the milk ducts, and as only a small proportion of the affected cows have disease of the udder, the danger from this 32 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. source was thought to be slight. It seems likely, however, that the udder is affected in a larger number of cases than has usually been admitted. It requires a very long and careful examination to deter- mine positively that the udder is free from the disease. The European statistics have usually given the proportion of udder tuberculosis as from 1} to 3 per cent of the total number of cases; but Pearson, in the examination of 1,200 tuberculous cows in Pennsylvania, found the udder affected in 8.75 per cent of the animals. Numerous investigations have also shown that milk may contain tuberele bacilli when there are no appreciable signs of tubercular disease in the udder. A few of the more striking of these may be mentioned. Bane” tested the milk of 21 tuberculous cows with nor- mal udders by inoculating 48 rabbits. Two, or 9.5 per cent, of these cows transmitted the disease. Later he injected 40 guinea pigs with milk from 28 cows affected with generalized tuberculosis and showed that virulent milk was being secreted by 4 of these animals, 3 of which on post-mortem examination were found to have lesions in the udder. By intra-abdominal inoculations of 28 guinea pigs with the milk of 14 tuberculous cows he found that 3 of the latter were excreting tubercle bacilli in their milk. The summary of these experiments shows that of 63 cows 9 gave virulent milk, and of this number 3 had tuberculous udders, leaving 9.5 per cent of the cows with normal udders producing infectious milk.” Ravenel ® experimented with 5 cows which reacted to tuberculin but showed no physical signs of tuberculosis. The udders in every case were free from disease so far as a careful inspection could reveal. The post-mortem examination of these cows confirmed the diagnosis made during life. He inoculated guinea pigs with a single dose, averaging 10 c. c. of milk from these cows. In the first series of experiments 4 out of 31 guinea pigs, or 12.9 per cent, became tuberculous. In the second series of experiments 5 out of 24 guinea pigs contracted tuber- culosis, a percentage of 20.8. In the third series, in which the milk of a single cow was employed, 1 guinea pig out of 8 became tuberculous, or 12.5 per cent. In these three series of experiments 10 guinea pigs out of 63, or 15.8 per cent, became infected by a single dose of milk from these cows which apparently had no disease of the udder. Rabinowitsch® and Kempner succeeded in producing tuberculosis in guinea pigs with the milk of 10 out of 15 tuberculous cows, or 66.6 per cent. Two of these cows were later found to have tuberculous udders, 3 showedadvanced generalized tuberculosis, while the remaining 5 animals were but slightly affected. The writers conclude that milk from cows with incipient tuberculosis, but without disease of the udder, may contain tubercle bacilli; also that in latent forms of tuberculosis the milk may prove infectious, although the cow may not present any clinical symptoms of tuberculosis; and therefore that milk from all cows reacting to tuberculin should be considered as at least suspicious. MATERIAL FACTS CONCERNING TUBERCULOSIS. 33 It is believed by Adami* that the cells of an actively secreting mammary gland of a cow can take up and discharge the tubercle bacilli without the animal showing any lesion of the lacteal tract. He and Martin examined the milk of 10 cows, and when these were killed the udders were subjected to niicroscopic examination with negative results. In the milk of 6 (60 per cent) of these cows tubercle bacilli were observed by the aid of the microscope. The milk from the cow showing the greatest number of bacilli was inoculated into 2 guinea pigs, and both died as a result of the infection. Twenty-nine guinea pigs and 26 rabbits were inoculated with varying quantities of milk, and 1 calf was fed for five months, but only 2 guinea pigs died of tuberculosis. Gehrman and Evans*' found tubercle bacilli in the milk of 15 out of 41 cows with sound udders, or 36.6 per cent. Guinea pigs inoculated with milk from 10 of these cows died of tuberculosis (24.3 per cent). Their final showing is that 16 of the cows, or 39 per cent, at one time or another, gave milk containing tubercle bacilli. The milk of 56 reacting cows which showed no signs of disease of the udder was carefully tested in various ways by Mohler and Norgaard.” One or more of the guinea pigs fed with milk from 9 different cows out of this lot succumbed to typical tuberculosis—that is, the milk of 16.07 per cent of the 56 reacting cows was found to be pathogenic to guinea pigs when fed to them. Of the experimental animals inoculated intra-abdominally in the first series, at least 1 guinea pig died of tuberculosis in each of six dif- ferent instances, showing that the milk of 10.9 per cent of the 55 reacting cows in this experiment was fatal to guinea pigs. In the second series of intra-abdominal injections, the milk from 7 individual cows out of 45 examined, or 15.5 per cent, was demonstrated to pos- sess virulent tubercle bacilli. By uniting these inoculation results, it is found that 11 out of 55 cows, or 20 per cent, secreted milk which transmitted tuberculosis to one or more experimental animals when injected into the peritoneal cavity. The combined results of the ingestion and inoculation experiments showed that the milk of 12 out of 56 reacting cows, or 21.4 per cent, at one time or another, during the experiment contained virulent tubercle bacilli. Specimens of the mammary glands from all the cows yielding this virulent milk were brought to the laboratory and histological exami- nation was made of them without finding any indication of tuberculosis. With one of these cows positive results were obtained in all of the tests—that is, by ingestion, by inoculation, and by miscroscopic examination of the sediment of the milk and cream—although but 7 of the 10 experimental animals fed and inoculated with the milk of this cow became-_tubercular, It was evidently a case in which the milk 1881—No, 88—06——3 . 34 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. was seriously contaminated. Special attention was given to the exami- nation of the udder of this cow and numerous serial sections were examined, with entirely negative results. “fhe results of these careful experiments prove that the milk from a considerable proportion of reacting cows contains the tubercle bacillus and is capable of producing tuberculosis in animals which consume it. The proportion of cows which yield such infected milk is much greater than the proportion which show tuberculosis of the udder. Whether the milk in these cases was actually infected within the udder or whether it became contaminated at the time it was drawn makes little practical difference. Every precaution was taken to pre- vent such contamination after the milk left the mammary gland, and if the bacilli floating in the air of the infected premises or dropping from the coats of the animals infected the milk in spite of the precau- tions that were taken, similar infection would certainly occur in ordinary dairy operations. It must be admitted, therefore, that the milk from tuberculous cows is often infected and dangerous when, so far as can be ascertained, the udder is in a normal condition. The milk from tuberculous herds is a frequent source of tubercu- losis in calves and pigs. The calves born in tuberculous herds are fed upon the milk produced by such herds during the early period of their lives, and a considerable proportion of them may be infected in that way. In dairies where butter is made, or from which cream is sold, the skim milk is commonly fed to pigs, and in other cases skim milk is obtained from creameries for feeding to calves and pigs, and the animals are often infected in this way. Pearson and Ravenel,” in treating of the ways in which tuberculosis may be spread, say that the mixed skim milk returned froma creamery to a healthy herd may be contaminated. This danger is so great that in some places (parts of Pennsylvania and New England, France, and Germany) it is the practice to heat skim milk to a temperature that will insure the destruction of the tubercle bacillus. In Denmark and Prussia such heating of skim milk and buttermilk is required by law. Several illustrations of this danger had recently come under the obser- ration of these authors. In one case a large herd was tested with tuberculin and found to be extensively diseased. Two of the cows had tubercular udders. This herd was used for the production of cream that was shipped to market, the skim milk being retained for feeding calves. It was the practice on this farm to remove the calves from their dams when they were three days old and keep them in a separate building distant from the cow stable. The dairy building and separator were located midway between the cow stable and the calf stable. After the cream had been separated the skim milk was carried on for the calves. When the cows were tested the calves were also examined, and it was found that while the prevalence of tuberculosis among the MATERIAL FACTS CONCERNING TUBERCULOSIS. 35 dairy cows was 75 per cent, all the calves reacted and were condemned. The post-mortem examinations of the calves revealed tuberculosis of the postpharyngeal lymphatic glands or lower digestive tract in all cases, indicating that infection had occurred through the digestive system and that it had been carried to these calves in skim milk. Only a small proportion of the calves dropped by tuberculous mothers are affected with tuberculosis at the time of birth. In other words, the cases of congenital tuberculosis are very rare. Klepp found at the slaughterhouse in Kiel among 4,068 calves that were slaughtered only 26 affected, or 0.64 per cent, and in a second series of investigations there were found 10 calves affected with congenital tuberculosis among 847, a proportion of 1.18 per cent. Héybere obtained similar results, having found 6 cases of congenital tuberculo- sis among 500 calves examined at the time of slaughter. According to the calculations of Klepp only 2.63 per cent of the calves dropped by tuberculous mothers are affected with congenital tuberculosis.” As an example of the proportion of calves found affected, Bang” gives the statistics of the small slaughterhouse at Aarhus, Jutland, where very careful examinations are made and where the cattle come from a district in which tuberculosis is very widely distributed. In the year 1903 there were found among 6,765 calves (3,279 quite young calves and 3,484 fat calves) 100, or 1.48 per cent, tuberculous (with 14 new-born calves the existence of congenital tuberculosis was discov- ered). Among 4,920 grown cattle there were 2,509 tuberculous, or 51 per cent. ~ It would appear from these figures that possibly not more than 1 per cent of the calves from tuberculous mothers are affected with tuberculosis at the time of birth. In very badly affected herds as high as 2 per cent of the calves may have congenital tuberculosis. Under any circumstances, it is plain that the great majority of calves contract the disease either from contaminated milk or from inhabiting the stables where tuberculous cows are kept. Bane” gives the following table showing the distribution of tuber- culosis according to age in 40,624 cattle tested for the first time in Denmark during the years 1898-1904: = | Number | Age when tested. j Number | “hich | Percent. | tested. | -oacted CalVESHUpsLOLOne Nalliny Cale reset). Sah tsk = devetchls =e steja aivaetstetes siete aie a 5, 599 675 12.1 Gatilestromone-hali LOM ryveaTs eons. oo dene oes, cel coms = emission ce iieae 7,744 2,129 DIED Ma Tu CeMOMOl a slOrZ seVew Use ase creek ta ate eae a Jace Pees ae Ss eee see eee 5, 047 | 1, 949 | 38.6 Cathlediromy22 TOO yCarsels os 2c soale Sere 2 cineca ls cine sie alocoie sia sacs aiaeteecin ais) 10, 350 4, 644 | 44.9 GAtTLCLOV ClronVyiCH Seamer reece anes na yee sone e cis cyan Abie. ols eereiucle Siero ee 11, 924 5, 724 | 48.0 ANGIGN) 2 sesbecesD poo es SES BAEC e Es Eon aR e eRe rone Hemme accesses, Bee teraie 40,624 | 15,121 | 37.2 This table shows that, in a country where from 45 to 48 per cent of the adult cattle are tuberculous, 12.1 per cent of the calves are affected by the time they are six months old. If 2 per cent of these calves 36 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. have congenital tuberculosis it follows that more than 10 per cent of them contract the disease from the milk which they drink or from the infected stables in which they are kept. During the second half year of the life of the animals an additional 15 per cent become infected. Probably the greater part of the infections during the first year result from contaminated food. These statistics, therefore, show the impor- tant réle played by infected milk as a disseminator of tubercular disease. Phelps,** of the Storrs (Conn.) Experiment Station, reports the results of experiments made there in feeding to calves the milk of tuberculous cows: During the greater part of the four years that 4 tuberculous cows were at the sta- tion the “milk of some or all of them was fed to calves. The results of the first two years’ feeding show that, while the milk of each of the 4 cows was fed to several calves in periods ranging from three months to one yearand four months, in no case was there any indication of disease in the calves during the feeding period. The calves were kept with the cows nearly two years. One of these calves responded to the tuberculin test about five months after the feeding period of sixteen months was ended, and was found upon post-mortem examination to be very slightly diseased. Two caly es, the offspring of tuberculous cows, were selected for a comparison of the infectiousness of pasteurized and raw milk. About hatf of the milk of 1 cow was heated toabout 170° F. and fed to her offspring, and the balance of the milk in its natural state was fed to the offspring of the other tuberculous cow. The calves were isolated from the cows. Neither of the calves responded to a tuberculin test made after a feeding period of about ten months. By a misunderstanding both of the calves were fed the unpasteurized milk of the cow for a period of three weeks (following the tuberculin test), after which they were turned out to pasture for about five months. Three weeks after being returned to the stable with the cows the calf which had been fed the pasteurized milk (except for three weeks) responded to the tuberculin test, while the other calf failed to respond until five months later. Two other calves were fed the milk of their dams from August and September, 1898, until the next June. At the end of ten months’ feeding in one case and nine and one-half in the other neither of the calves responded to the test. One calf was at pasture from June 24 to November 13, while the other remained in the stable with the cows. Both responded to the test on December 2 following, three weeks after one of the calves was returned from the pasture. Two more calves were fed the milk of the 2 other cows. Both had tuberculous mothers. One was kept in the stable with the cows, and after being fed the milk of cow No. 1344 for a period of ten weeks responded to the tuberculin test. The other was fed the milk of its dam (No. 1348) while isolated in a room in another part of the barn. After a feeding period of nearly three months this calf responded to the tuberculin test. Three other calves from nontuberculous cows were selected early in May, 1900, and placed in a small pasture near the station barn. Calf L was fed the milk of No. 1337, calf M the milk of No. 1341, and calf N the milk of No. 1348. All prac- ticable precautions were taken to prevent the transmission of the disease in any way except by the milk. The calves were tested May 24-25, about three weeks after the feeding began, and again September 28-29, after having been fed over four and one- half months. None of the calves responded to either test. The calves were not fed milk after the September test but were kept isolated from the cows. Calf M died November 29, and an examination by the station veterinarian revealed a congested condition of the stomach, kidney, and bladder, indicating some form of poisoning. An examination of the lungs also. demonstrated the existence of tuberculosis, there being a tuberculous nodule in the right lung, calcified, and the mediastinal lym- phatic being tuberculous. The two remaining calves failed to respond to a tuber- culin test in February, 1901, and in May were sent to pasture with some other stock. Thus in the first feeding test 1 calf out of several became tuberculous, and in the four succeeding tests 7 out of 9 eventually became tuberculous. The 2 which did not respond to the test may or may not have been diseased. The uncertainty of depending upon repeated tuberculin tests in such cases is shown by the last- mentioned experiment, in which no tuberculosis would have been found had it not been for the accidental death of one of the calves. Some of these calves may have been infected through cohabitation, but in any case the large proportion of infection shows the danger of having tuberculous cows In a herd. MATERIAL FACTS CONCERNING TUBERCULOSIS. oO SPREAD OF TUBERCULOSIS FROM DISEASED TO HEALTHY CATTLE The rapid and widespread dissemination of the disease by the sale of breeding stock from tubercular herds has been pointed out by Russell and Hastings.** Where the disease establishes itself in herds that are sold for breeding purposes the danger is much increased, for animals from such sources are much more apt to be widely disseminated, since they generally serve as a foundation for the breeding up of common stock. The State of Wi isconsin, as well as other Northwestern States, has suffered in this regard very severely from some of its finest breeding herds. One herd in particular in this State has had anything but an enviable record in this mat- ter, for it has been determined that tuberculosis has broken out in at least 16 herds to which members of this original herd were sold. While it can not be proved that the origin of the disease in each of these 16 cases could be traé¢ed to the animals originally purchased, yet itis noteworthy that ina considerable number of cases the first animals to show evident symptoms of the disease were those that were introduced from this badly diseased herd. Not only were a number of fine herds in Wisconsin infected from this source, but the contagion was also spread, in a number of cases, to Minne- sota and Iowa. Schroeder and Cotton® have made experiments to test the rapidity with which tuberculosis spreads in a stable from diseased to healthy cattle. Seven healthy cattle and 3 tubercular cows were confined in a stable containing 10 box stalls, which were separated by solid 2-inch plank partitions 6 feet high. Five of the healthy cattle and the 3 tuberculous cows occupied different stalls each day, in a rotation which exposed each of the healthy cattle equally to the 3 dis- eased cows. Two of the healthy cattle occupied stalls near the center of the stable and were at no time allowed to enter other stalls or to come into closer contact with any of the other cattle. Two and one-half months after the beginning of the experiment | of the 3 tuber- culous cows was removed from the stable, and 2 other and more sev erely affected cows were introduced. One of these tuberculous cows died after it had been in the stable two months, and was found to be affected with generalized tuberculosis, but without disease of the udder or lymph glands associated with or near the udder. All of the exposed cattle were tested with tuberculin at the beginning of the experi- ment and found to be free from tuberculosis. The experiment began January 27, 1903, and the exposed cattle were tested with tuberculin on June 30 following. The two animals which had been confined to their stalls were a yearling bull, which reacted to the last test, and a 6-year-old cow, which did not react. Both ‘animals were found tuberculous when killed and examined August 8, 1903. In the bull the posterior mediastinal glands were slightly enlarged and contained numerous small recent foci of tuberculosis. The anterior mediastinal glands were greatly enlarged and filled with foci of tubercular material, and the bronchial glands contained several small foci of recent tubercular disease. The cow also was diseased, having several of the mediastinal glands greatly enlarged and thickly sprinkled with small tubercular nodules, recent in character, and, in addition, several small recent areas of tubercular disease scattered through the lung. Two heifers, 1 six months old and | eighteen months old, both in good condition, were made to occupy a different stall each day in order that they might be exposed equally to each of the tuberculous cows. When tested with tuberculin on June 30 both reacted. Post-mortem examination of the younger animal showed the left principal lobe of the lung adherent to the chest wall and near the adhesion a tuber- culous nodule in the lung tissue about 1 inch in diameter. The anterior and posterior mediastinal glands, the “bronchial glands, and the lymph glands about the root of the tongue were ereatly enlarged and either entirely tubercular or thic kly sprinkled with minute tubercular foci. Several of the mesenteric lymph glands were con- verted to the extent of half of their substance into tubercular material, and a num- ber of other mesenteric glands were affected, as were also the glands at the brim of the pelvis in the abdominal cavity. The lesions were all of comparatively recent origin. The older heifer had one small focus of tubercular disease in the left prin- cipal lobe of the lung, and sprinkled over various portions of the pulmonary pleura of the right principal lobe of the lung were numerous tubercles with corresponding tubercles on the costal pleura, The pulmonary surface of the diaphragm was 38 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. sprinkled with numerous small tubercles, and the various lobes of the lung were adherent to each other and to the diaphragm by means of tissue containing many tubercles. The appearances were typical of pearl disease in cattle. Three other cattle were exposed in the same manner as the 2 just described, but these had previously been given intravenous injections of dead or living tubercle cultures. One of these, a bull calf six months old, had 20 ¢. ¢. of dead ‘culture of human origin injected into the right jugular July 12, 1902, and _at the beginning of this experiment was in good condition and gave no reaction. When tested June; 30, 1903, it reacted, and on “post: -mortem examination tubercular deposits were found in the anterior and posterior mediastinal glands, while the lymph glands back of the pharynx were five times their usual size and completely tuberculous. There were also a number of recent tubercular foci in the liver. The second animal, a heifer calf about four and one-half months old, had received in the right jugular 20 c. ¢. of dead bovine tubercle culture July 19, 1902. This animal was also in good condition and failed to react at the beginning of the present experiment. When tested June 30, 1903, she gave a marked reaction. She was slaughtered and examined August 5, 1903, at which time there was found tuberculosis of the mediastinal and bronchial glands and of one mesenteric gland. The third animal of this group was a cow about two years old. This animal had received injections of 10 c. c. each of moder- ately virulent human tubercle culture into the right jugular vein on July 19, August 6, August 20, September 20, and October 7, 1902. When admitted into this experi- ment, “January 2 27, 1903, she looked thin and unthriity, but failed to react. She also failed to ae to the test of June 30, 1903. Killed and examined, August 6, 1903, the entire lung was found to be sprinkled with minute white nodules, having an appearance similar to that observed on several occasions after the injection of human tubercle into the veins of cattle. No tuberculous lesions were found in other parts of the body, and the disease in this animal was undoubtly caused by the injections of the cultures of human bacilli. The rapidity with which tuberculosis spreads in stables occupied by tuberculous cattle is shown with particular emphasis by the two cattle which became tuberculous without actual contact with the tuberculous cows and while standing in stalls which were separated from the other stalls by solid partitions 6 feet high. The distribution of the lesions indicate that the germs of tuberculosis in stable infection are more commonly respired than ingested with food. This experiment clearly shows that cattle can not be protected from tuberculosis when in the stables with tuberculous cattle, even when each animal is carefully restricted to its own individual stall. THE EFFECT OF INSANITARY CONDITIONS. The ideal conditions for health and for resistance to the tuberculosis contagion are life in the open air and an abundant supply of nutritious food. The greater the departure made from these ideal conditions, the more is the development of tuberculosis favored. At the same time it should be remembered that this disease will not appear in an animal unless the tubercle bacillus has gained entrance to its tissues, and this bacillus can not originate in a stable, no matter how insanitary its conditions may be. The tubercle bacillus, like other forms of liv- ing things, must come from a preexisting germ of the same species; and as it grows only in the body of an animal, it must be transported in some manner from a diseased animal to a healthy one before the latter can contract the disease. These are foundation principles which are thoroughly established and which must be borne in mind in han- dling animals for the prevention or the suppression of tuberculosis. MATERIAL FACTS CONCERNING TUBERCULOSIS. 39 Life in the open air is not always sufficient to prevent infection with tuberculosis or to cure animals that are already affected by it, but its influence is favorable and reduces the chances ef infection to the small- est proportion, while at the same time it places the diseased animal under the best conditions for its recovery. In most stables the condi- tions of life are radically different from what they are in the open air. It is only necessary to make the most casual inspection of the ordinary stable to assure oneself that the conditions of life there are unfavor- able in the extreme. Ventilation. —Most stables have no provision for ventilation. Any air which enters them must come through the doors or the walls of the buildings; either there are drafts of air upon the animals, favoring the production of colds and catarrhs, or there is an insufficient supply of oxygen. The circulation of pure air in a stable furnishes an abun- dant supply of oxygen, which increases the resisting powers of the animal, and it also serves to carry away dust and other impurities which may be floating in the atmosphere of the stable. Where there is no ventilation disease germs carried into a stable are likely to remain there until they infect the animals. Where there is little ventilation stables are almost always damp, and such dampness favors the preser- vation of the bacilli and tends to the production of catarrh in the air tubes of the animals, which is a condition favorable for the lodgment of these germs. Tuberculosis is most frequent with people, as well as with animals, who are crowded together in small and poorly ventilated quarters. An abundant supply of fresh air in the stable acts favorably in several ways: First, it isa means of supplying the animals with a proper amount of oxygen for carrying on the functions of their bodies; second, the circulating air carries away the carbon dioxide and the moisture given off from the animals’ bodies, and leaves the stables dry and healthful; third, the air currents also carry away bacteria of all kinds which may be floating in the atmosphere of the stable, and in that way they reduce the chances of infection; and, fourth, fresh air and dryness are unfavorable conditions for the preservation of bacteria, and, consequently, well-ventilated stables are not so easily infected as others, and the infection dies out more readily in them. Light.—lt is just as desirable that there should be ample provision to let light into a stable as that there should be ventilation. The direct rays of the sun are of especial value for destroying tubercle bacilli and for increasing the resistance of the animals to their attacks. In addition to this the sun’s rays aid in drying and disinfecting the stable. Light is also necessary to enable those who care for the stable to see the dust and filth and to put it into proper sanitary condition, Dark stables are almost universally dirty, damp, and unhealthful. Pearson and Ravenel” say with reference to this subject that— It has been shown by Migneco, Straus, and others that tubercle bacilli are destroyed by light in a time that is in proportion to the intensity of the light and inversely as the thickness of their protective coating. In Migneco’s experiments sputum con- 40 TUBERCULOSIS OF THE FOOD-PRODUCING ANIMALS. taining many bacilli were spread out on linen or cotton cloth and then exposed to sunlight. Subsequently the cloth was washed in sterile water and the wash water was injected into the peritoneal cavities of experimental animals. The virulence of the germs was greatly reduced in from ten to fifteen hours and when the layer was not too thick they were completely destroyed in twenty-four to thirty hours. Sunlight has a decided effect on the chemical processes that take place in living tissues. In the case of plants this is very marked. Dammann states that animals expire smaller quantities of carbon dioxide at night than during the day. Accord- ing to the experiments of Platin, which were made on rabbits, the increase in oxygen consumption and in carbon dioxide excretion under the influence of light is from 13 to 14 per cent. Dammann calls attention to the fact that this result is in full accord with the general experience that animals fatten best in dark stables, and it is also noticed that "animals kept in dark places for long periods become sluggish. The pallor that is characteristic of miners, stokers on ocean vessels, and prisoners is also due to the absence of light. In darkness there appears to be a checking of the metabolism and tissue change, an indolence of excretory functions. De Renzi has made some experiments to determine the effect of direct sunlight on tubercular processes. He inoculated 8 guinea pigs with tuberculous sputum and afterwards placed half of them in a glass box and the others in a wooden box. Both boxes were ventilated from below and were placed in the sun. The animals in the wooden box died on an average of twenty-seven days after the inoculation, while those in the glass box lived an average of fifty-seven days. Similar experiments have been made in the laboratory of the Pennsylvania live stock sanitary board, and it has been shown that light prolongs the life of a tubercular animal. Cleanliness.—A stable must be clean in order to be sanitary. Cleanliness is the first principle of sanitation, and it must be contin- ually kept in view. Not only must the filth on the surface of the floors be removed, but there must be no channels by which it can gather between or beneath the flooring to ferment, putrify, and =lhtes the atmosphere with noxious gases. The dust which gathers upon the walls is often even more objectionable than the filth upon the floors. In infected stables the dust is certain to contain tubercle bacilli, and these are in a condition to be easily floated in the atmos- phere and breathed into the animals’ lungs.