50 MORPHOLOGY OF THE BACTERIA. 



they exhibit the brownien movement, are t easily- 

 enough distinguished from Micrococci by optical 

 signs, their angular form, their less refractive 

 power, and finally by their reaction with certain 

 chemical agents ; above all if they are mineral 

 substances, crystalline bodies, etc. 



It will not be the same with molecular granules 

 of organic nature. They have as common charac- 

 ters, their rounded form, their notable refractive 

 power, movements. Nevertheless, their form is 

 less regular, more angular, their color variable, their 

 refractive power always less. In doubtful cases, 

 Tiegel has given a method which enables us to dis- 

 tinguish them from Micrococci. It consists in 

 warming the glass slide which supports the cor- 

 puscles under examination, if they are " Coccos," 

 they are seen to move in a manifest manner. 

 This does not occur in the case of molecular gran- 

 ules. 



It is these productions which render it very 

 difficult to observe the phenomena which occur 

 during the coagulation of milk. The caseine sep- 

 arates in the form of extremely minute globules 

 having a very rapid molecular movement. But 

 we may distinguish these from bacteria by the 

 use of liquor potassae, which dissolves the former 

 without attacking the latter. 



As another example of pseudobacteria, I will 

 mention, after Cohn, the form which fibrine as- 

 sumes when it separates from the plasma of the 

 blood. It disposes itself in very slender filaments, 

 closely resembling filamentous bacteria. 



