50 MORPHOLOGY OF THE BACTERIA. 



they exhibit the brownien movement, are easily 

 enough distinguished from Micrococci by optical 

 signs, tiieir 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. 



