128 THE COMMON SENSE OF THE MILK QUESTION 



time and led many investigators, in Europe and this 

 country, to make experiments and investigations along 

 the lines indicated by Dr. Smith's work. Few are 

 the workers in this field of research who have not 

 given special attention to the differences which char- 

 acterize the two varieties of tuberculosis, and the 

 result of their combined efforts may be briefly sunmied 

 up as follows : There are certain physical differences 

 to be noted, the human bacillus being long and slender 

 and the bovine bacillus thicker and shorter. The 

 bovine bacillus also stains more evenly in the labora- 

 tory. The principal difference, however, is not physi- 

 cal but pathological. While there are some animals 

 which seem to be equally susceptible to the attacks 

 of both kinds, — notably guinea-pigs and swine, — 

 other animals are almost invariably more susceptible 

 to the bovine variety than to the human. This 

 is especially true of monkeys. There seems to be no 

 case in which an animal has been found more sus- 

 ceptible to the human tubercle bacillus than to the 

 bovine, and it is concluded, therefore, that the bovine 

 bacillus is much more virulent than the human. This 

 is the opinion of our foremost American investigators, 

 as well as of the British Royal Commission appointed 

 to investigate the subject, under the leadership of Sir 

 Michael Foster, professor of physiology in Cam- 

 bridge University." 

 The discovery made by Dr. Theobald Smith had 



