Heredity and Predisposition. 521 



tuberculous do not live and are frequently born prematurely. 

 Calves several weeks of age are rarely found affected with 

 tuberculosis and among slaughtered calves the percentage of 

 diseased animals usually does not reach 1/2%, while tuberculin 

 tests even m badly infected herds rarely reveal more than 10 

 or 15% of infected animals under 6 months, in spite of the 

 fact that these animals have had abundant opportunity to be- 

 come infected. The most convincing proof against the effects 

 of heredity in the transmission of tuberculosis is furnished by 

 the fact that the offspring of tuberculous cows remain healthy 

 and free from tuberculosis if properly guarded against infection 

 after birth. 



The first case of hereditary tuberculosis was established by Johne when he 

 demonstrated tubercle bacilli and tubercles in the lungs and liver of a fetus eight 

 months of age. Since then similar eases were reported by others (Gsokor, Nocard, 

 MacFadyean, etc.). Up to the year 1909 Albein had compiled reports of 107 similar 

 eases, 91 of which were unquestionable. At a later date Hoyberg reported 6 cases 

 of congenital tuberculosis among 500 calves examined immediately after birth and 

 Bergman reported 108 personally observed cases, among them 4 fetal; the others 

 in calves not exceeding three days of age. These were observed during the years 

 1904-8 in the abattoir of Malmoe (0.42% of all slaughtered calves). 



Among slaughtered calves up to five months of age, Klepp of Kiel found 

 0.64-1.18% tuberculous. In a badly infected region of Jutland, in Aarhus, Knudsen 

 reported 0.3% to be tuberculous. Stroh's estimates for 1901 and 1902 gives for 

 Bavaria the following figures: For every 100 tuberculous slaughtered cows, 6-7 

 tuberculous calves; for every 100 cows with advanced tuberculosis, twenty-five 

 tuberculous calves, but some of these were evidently cases of extra-uterine infection 

 (see statistics on page 502). 



In the course of his tuberculin test work in Denmark, Bang found among 24,267 

 calves under six months, 10.6% tuberculous. The author's own observations on 544 

 calves under six months showed 59 tuberculous, that is, 10.8%. In one badly infected 

 herd 15 out of 48 calves or 31.2% reacted. In calves of this age, however, the 

 results of extra-uterine infection are already evident, because according to Nocard 

 and Bang the percentage of reactions does not exceed 5% during the first few 

 weeks of life, the authors themselves have observed that in one herd where 44.8% 

 of all cows were infected only one out of 04 sucking calves gave a positive tuberculin 

 reaction (1.6%). 



In congenital tuberculosis of calves the periportal lymph glands are 

 always involved. Next in frequency are the liver, the mediastinal and 

 the peribronchial glands, then the lungs and, in exceptional cases only, 

 other organs (Klepp, Rievel). This localization points to the fact that 

 infection takes place in a late stage of embryonic existence, through the 

 placental circulation from the dara. (Bang is of the opinion that 

 isolated tuberculosis of the posterior mediastinal glands has the same 

 origin.) In regard to the rare occurrence of congenital tuberculosis 

 compared with the comparative frequency of tuberculosis of the uterus 

 of cattle, it is probable that infection of the foetus occurs only in far 

 advanced tuberculosis of the uterus or if the cotyledons and chorion villi 

 are affected (Kockel and Lungwitz have demonstrated tubercle bacilli 

 in the villi of the chorion and Burgmann, demonstrated them in three 

 instances In the placenta). 



Without disease of the placenta or the fetal envelopes it would 

 hardly be possible for the bacilli to pass from the mother to the fetus. 

 Although Ravenel and Bucher each reported a case of congenital tu- 

 berculosis in the calf where the uterus of the dam was healthy, very 

 slight tuberculous changes could certainly have escaped macroscopic 

 observation. 



