MORPHOLOGY AND BIOLOGY OF BACTERIA. 23 



speculation, a spindle-shaped figure results, which is known 

 as a clostridium. 



At a later stage the body of the bacillus disintegrates, 

 and the spore is set free. If this finds its way into a suita- 

 ble nutritive medium of dead or living matter, it germinates, 

 becomes a rod, the rod multiplies by dichotomy, and the 

 whole process again terminates with the formation of new 

 spores. The manner and the method in which the spore 

 becomes transformed into a rod vary among different bac- 

 teria. Full details, in so far as they are of importance for 

 clinical bacteriology, will be discussed in the special section 

 of this work. In general the process of development is 

 such that the spore first takes up water, then swells, next 

 doubles in size, and loses its marked refractive property. 

 The spore-membrane ruptures in the center or at one pole ; 

 the young bacillus slips through the rent, retaining for 

 some time the capsule of the permanent body. 



Spore-formation and spore-germination take place only 

 within certain temperature-limits, which differ for each indi- 

 vidual bacterium. In the mode of sporulation just de- 

 scribed the spore develops from the interior of the proto- 

 plasmic ground-substance of the rod, and this form of 

 fructification is therefore designated endogenous spore-forma- 

 tion, in contradistinction from arthrogenous spore-formation, 

 where individual segments of the cell-chain assume spore- 

 qualities without passing through any intermediate stage. 

 In external appearance these particular cells may differ in 

 no respect from other bacteria of the same chain. Some- 

 times they become somewhat larger and brighter and more 

 highly refractive and surrounded by a firmer capsule. 



Attempts have been made, upon the basis of these vari- 

 ations in fructification, to divide bacteria into two great 

 classes (i) those with endogenous spore -formation (endo- 

 sporous bacteria] and (2) those with arthrogenous spore- 

 formation (arthrosporous bacteria). Among the latter class 

 the cocci principally are grouped. However desirable 

 it might be to classify the bacteria according to an intrinsic 

 principle, it must be emphasized that the classification 

 mentioned appears at least premature, inasmuch as our 

 knowledge concerning the arthrogenous spores is as yet 

 but slight and uncertain. 



The spores represent permanent forms of the bacteria. 

 Owing to the concentrated nature of their plasma, they are 



