35° MICRO-ORGANISMS AND DISEASE [cHAP. 



cal, or rod-shaped granules; between the granules the 

 sheath is empty, but these empty places are not to be 

 taken for bright spores, as is done by some observers, nor is 

 it proved that the above granules are spores. That the 

 tubercle bacilh contain spores is proved by numerous 

 experiments of drying and heating, to be detailed below, 

 but what the character of these spores is, and how they 

 appear in the bacilli, has not been satisfactorily shown. In 

 bovine tubercular matter prepared in the same manner the 

 tubercle bacilli are distinctly shorter and thinner, and though 

 I do not for a moment question the fact that some tubercle 

 bacilli of human tubercle are as short and thin as those of 

 bovine tubercle, I am confident from numerous observations 

 that the majority of the human tubercle bacilli of sputum 

 are longer and thicker than those of bovine tubercle ; 

 besides, in preparations stained in the above manner alike, 

 the segregation of the protoplasm within the sheath, though 

 also present in many tubercle bacilli of bovine tubercle, is 

 not so general and uniform as in those of human tubercle. 

 But these minute differences need mean nothing more than 

 differences due to the different soil on which the bacilli 

 were reared. Such morphological differences in size and 

 aspect in one and the same species of microbes are well 

 known to occur in other instances if the microbe be 

 cultivated in different soils. When the tubercle bacilli from 

 whatever source (bovine, human, or from articially infected 

 animals) are passed through the rabbit or the guinea-pig, in 

 these animals the new crop of bacilli all appear to be 

 morphologically the same. 



