DESCRIPTIONS OF PATHOGENIC BACTERIA. 197 



velops delicate white fleecy clouds which, be- 

 come diffused through the medium. In agar 

 yellow-white colonies limited in extent, arise. 

 The small rods are like needle-shaped crystals, 

 0.8-i.u long, O.I-0.2/'- thick, and are often 

 grouped in pairs ; they are not motile. 

 These bacteria are interesting from the fact 

 that LofHer used them successfully in com- 

 bating a plague of mice in Thessaly. The 

 cultures were smeared upon bread which was 

 distributed over the fields so the mice might 

 feed upon it, the bacteria having proved to be 

 harmless for all the animals experimented 

 upon save mice. 



Tuberculosis. Tumors in connective tissue 

 may occur in the form of nodules or tubercles 

 varying from the size of a millet seed and un- 

 der to the size of a pigeon's egg. By the term 

 tuberculosis, however, is understood a definite 

 kind of nodule formation which shows, besides 

 small cells, epithelioid cells (Fig. 25 E), and 

 often giant cells, and is caused by an organism 

 studied microscopically by Koch and Baum- 

 garten in 1882. The organism was also cul- 

 tivated, and was more accurately and fully in- 

 vestigated by Koch (Fig. 28.). The rods are 

 often plainly enclosed in a sheath, inside of 

 which are found, along with the rods, whole 

 series of cocci formed as the result of plasmo- 



