DISEASES OF CATTLE 263 



One statement which has an important bearing on the intra- 

 venous methods of producing resistance against tuberculosis must 

 be added here. All our cattle treated with intravenous injections 

 of tubercle bacilli showed, on careful post-mortem examination, 

 some pulmonary lesions, such as thickening of the pulmonary 

 connective tissue, adhesions between the lobes of the lungs and of 

 the lungs to the chest wall and diaphragm, to be sure only very 

 slight in most instances, but which could be accounted for in no 

 other way than as remnants of the disturbance caused by the in- 

 jected bacilli. This alone constitutes a condition which should 

 receive further attention before a system of bovo-vaccination re- 

 quiring the intravenous injection of living cultures of tubercle 

 bacilli is practiced on a wholesale scale, and, in conjunction with 

 what we know about the retention of tubercle bacilli in the tissues 

 after injection and the uncertainty about the manner and state 

 in which they leave the body, should teach us to proceed cautiously 

 in the adoption of protective methods, notwithstanding the fact 

 that the results obtained prove conclusively that actual, strong re- 

 sistance to tuberculosis can be established by using them. 



COMPARISON OF THE FOREGOING METHODS. 



From the brief accounts that have been given we see that 3 

 of the 9 cattle treated according to the method of Von Behring 

 and afterwards exposed contracted tuberculosis, that 1 of the 9 

 cattle treated by the method of Pearson and afterwards exposed 

 contracted tuberculosis, and that of 14 checks or untreated control 

 animals 12 became infected on exposure. 



Of the 8 animals that received injections of bovine tubercle 

 culture subcutaneously into the ends of their tails (4 old and 4 

 young animals), all but 1 young animal contracted disease as the 

 result of the injections. The one that escaped disease from the 

 injection also resisted tuberculosis on exposure. 



Of the 5 cattle that received human culture injections into 

 the ends of their tails, 2 became immune without inoculation dis- 

 ease, 2 were immune but had slight inoculation disease, and 1 

 had both inoculation and exposure disease. The injection of tu- 

 bercle cultures under the skin of the neck of animals caused them 

 all to contract tuberculosis. The several methods may be com- 

 pared as follows: 



Von Behring cattle, 66 2-3 per cent successfully protected for 

 a period approximating 2 years. 



Pearson cattle, 88 8-10 per cent successfully protected for a 

 period approximating 2 years. 



Bovine cultures, tail, protected 12^ per cent. 



Human cultures, tail, protected 40 per cent.* 



Injections under skin protected per cent. 



The above percentages can best be valued by comparing them 



*It should be borne in mind that the human cultures injected in the tail actu- 

 ally protected 80 per cent, of the cattle treated against the injection in the en- 

 vironment to which they were exposed. 



