No. 6. DEPARTMENT OF AGRICULTURE. 12? 



The ditiereuces noted between tuberculosis ot man and tubercu- 

 losis of cattle are scarcely greater than those noted between the 

 latter and tubrculosis of swine, jet nothing is easier than to infect 

 swiue with the milk or other products of tuberculous cattle. The 

 infection here is bv natural methods, and in fact is most ofteu noted 

 where nothing was further from the wishes or intentions of the un- 

 conscious experimenter. The origin of the infection is unquestion- 

 ably bovine, yet the disease produced differs markedly, but not es- 

 sentially, from that seen in cattle. The evidence then leads us to 

 conclude that such differences as are commonly seen between human 

 and bovine tuberculosis are iu no sense essential. 



Bacteriologic Evidence. Morphology and Cultural Characteristics 

 of Human and Bavine Tubercle Bacilli. — That there were certain 

 differences to be observed in cultures of the tubercle bacillus isolated 

 from man and from cattle was shown by Dr. Theobald Smith in 181)6, 

 who conrirmed his first observations in 18JJ8, his human cultures being 

 almost always obtained from sputum. A study similar to Dr. Smith's 

 has been carried on at the laboratory of the State Live Stock Sanitary 

 Board of Pennsylvania for several years, the material for the cul- 

 tures being obtained from divers sources. With one exception, which 

 was isolated from sputum, all the human cultures have been ob- 

 tained from internal organs, especially the lungs and mesenteric 

 glands. Two of the bovine cultures have been found in milk, the 

 others coming from internal organs or glands. The result of our ob- 

 servations, which have agreed closely with those of Dr. Smith, is as 

 follows: The morphology of the bacilli in cultures of bovine origin 

 is more unifoiin and constant than in cultures from man. The bovine 

 bacilli are thick, straight, and short, seldom more than two inches in 

 length, and averaging less. In the early generations many indivi- 

 duals are seen which are oval, their length not more than double 

 their breadth. They stain evenly and deeply with carbol-fuchsin, 

 beading being almost always absent from young cultures and often 

 from old ones. 



The human bacilli are, as a rule, much longer from the start, and 

 tend to increase in length at once in sub-cultures. They are gen- 

 erally more or less curved, some cultures showing S-shaped forms. 

 They stain less intensely with carbol-fuchsin, and beading is gen- 

 erally seen, even in earl}- growths. 



The above characteristics are most marked and most persistent 

 in cultures grown on blood-serum. On glycerin agar, glycerin bouil- 

 lon, and glycerin potato the bacilli from the two sources approach 

 each other in cultural features and morphology much more closely, 

 and by continued cultivation the dilfere-nces tend to become obliter- 

 ated. Bovine cultures are more dilficult to isolate than human, are 

 apt to grow as discrete colonies in the first culture, and for several 



