No. 4.] CATTLE COMMISSIONERS. 577 



In these three experiments the conditions were kept as nearly 

 uniform as was possible, with the means at my disposal It was 

 unfortunate that an animal as old as No. 88 (bovine IV.) should 

 have been included ; it is also to be regretted that the swine cult- 

 ure was about a year old when used upon cattle. Undoubtedly 

 the total absence of any lesions following the injection of the 

 Nasua culture is partly due to the age of the culture. Leaving 

 these aside, the remaining parts of the test appear to me to be of 

 sufficient uniformity and accuracy to justify us in drawing certain 

 preliminary inferences. We may now maintain that bovine 

 tubercle bacilli and human bacilli as found in sputum are not 

 identical. The difference in their action upon cattle is reinforced 

 by certain differences in the bacilli themselves and their effect 

 upon rabbits, as will be detailed in a fuller report. 



What the significance of these divergencies is, what influence 

 they have upon the transmissibility of the disease from cattle to 

 man, we are unable at present to state with any degree of cer- 

 tainty. That they do have some effect must be admitted, in view 

 of results of studies upon other species of pathogenic bacteria. 

 Their precise bearing needs careful investigation. 



These studies will, I think, warrant one inference, however ; 

 that is, that human sputum cannot be regarded as specially dan- 

 gerous to cattle, nor can it be looked upon as a factor in the 

 introduction of tuberculosis into a healthy herd of cattle. Even 

 if the tubercle bacilli of cattle and of man are very closely related 

 and have the same ancestry, as we all must admit, if we regard 

 the two as mere varieties, which may eventually under very favor- 

 able conditions pass one into the other, the condition in which the 

 bacillus leaves the lungs in sputum is evidently such as to inter- 

 fere, under ordinary circumstances, with any development in the 

 bovine body. It would fall a speedy prey to destruction. 



I refrain, for obvious reasons, from drawing the conclusions 

 that all human tubercle bacilli are like those existing in the sputum 

 of phthisis. On this point we are still in the dark. 



The following pages give a concise tabular account of the cult- 

 ures employed in these investigations, of the animals upon which 

 they were tested and the temperature records of the third experi- 

 ment. Those of the second experiment, as stated above, reveal 

 no essential differences between the different animals, and are 

 therefore omitted. 



