28 OUTLINES OF BACTERIOLOGY 



periphery of the area by several strands of protoplasm. This is 

 diagrammatically represented in Fig. 42&. In the next stage this 

 space stains more deeply than the surrounding area. No doubt 

 this is due to the fact that a large portion of the protoplasm has 

 been concentrated into it (Fig. 42c). After this, the periphery of 

 the young spore, as we may now term the area into which con- 

 centration is taking place, begins to take on a deeper stain, showing 

 that a spore membrane is being formed (Fig. 42f/). A stage, further 

 in development, shows a still more definite membrane. In conse- 

 quence of the presence of this membrane, spores take up stains very 

 slowly and the ordinary staining methods never accomplish the 

 staining of the contents of the spore (Fig. 42e). The last stage is a 

 still further elaboration of this membrane, which is now seen to consist 

 of two coats, an inner thin coat called the intine, and an outer tough 

 coat, the extine, which often exhibits markings on its outer surface. 

 The endospore is now mature. The remainder of the cell at the com- 

 pletion of this development is, in most cases, empty, the endospore 

 being often seen lying free in an empty cell (Fig. 42e) In some 

 cases, however, the protoplasm is not all used up in the formation ot 

 the spore, for motile individuals, each containing a spore, may be seen 

 occasionally. It follows that in these cases there must be protoplasm 

 inside the cell, for the cilia could not otherwise be functional. 



Usually during spore formation there is no change in the bacterial 

 cell (Fig. 42e), as, for example, in Bac. hirtus and Bac. anthracis, but 

 in some species a swelling takes place at, the point where the spore 

 is being formed. Thus, in one of the bacteria which excrete butyric 



FIG. 43. Bac. araylobacter. FIG. 44. Spore formation in 



Bac. tetani. 



acid, Bac. amylobacter, the various forms shown in Fig. 43 may be seen 

 during spore-formation. In Bac. tetani, which causes the lock-jaw 

 disease, the swellings are invariably at one of the ends (Fig. 44), this 

 characteristic being very useful for purposes of identification. Bac. 



