286 ANNUAL REPORT OF THE Off. Doc. 



THE COMPARATIVE VIRULENCE OF THE TUBERCLE BAC- 

 ILLUS FROM HUMAN AND BOVINE SOURCES.* 



By MAZyCK P. KAVlfiNEL, M. D., Lecturer on Bacterioloyy, VeUrinary Department, University of 

 Pennsylvania; Bacteriologist of the State Live Stock Sanitary Board of feunsylvania. 



The relation existing betweeti the various types of the tubercle 

 bacillus found in man and in the lower animals, has been the subject 

 of much discussion for several years past, and studies of the mor- 

 phology, biology, and virulence have been undertaken with the ob- 

 ject of determining whether or not constant differences could be de- 

 tected in the organism from these two sources sufficient to justify 

 their classification as distinct species. 



From a purely practical standpoint, the question is narrowed to a 

 study of the bacillus as found in man and in cattle, and in the de- 

 termination of the relation they bear to each other. The importance 

 of this study is immense, not only to the physician, anxious mainly 

 for the protection of his clients, and to the general public who look 

 to the medical profession for guidance in such matters, but perhaps 

 even more so for those who are concerned in the framing of laws 

 and direction of public measures looking to the suppression of tuber- 

 culosis in man and animal. Efforts in this direction often meet 

 with strong opposition, and extreme statements are made oo very 

 scanty evidence, which render the task of the hygienist much more 

 difficult, and may result in the failure of his purpose. The lack of 

 positive and authoritative knowledge in regard to this matter has in 

 recent years led to the adoption of retrograde measures in several 

 places. The problem is one that can be entirely cleared up only by 

 a loog series of observations and carefully conducted experiments, 

 which are tedious, exacting, and require a considerable lapse of 

 time before results can be had. The correct interpretation of these 

 results is, in many cases, not an easy matter. 



The identity of the tubercle bacillus as found in the mammalia 

 went unquestioned for many years, and laws for the prevention of 

 the transmissioo of the bacillus of cattle to man have been based 

 mainly on this belief. In America, Dr. Theobald Smith was the 



♦Read before the British Congress on Tuberculosis, Section on Pathology and 

 Barterlology, London, July 23-26, 1901. 



