THE LIFE HISTORY OF BACTERIA. 55 



The prime object of this spore-wall is to protect the proto- 

 plasmic contents against conditions which would otherwise 

 destroy the life of the organism. The exact chemical com- 

 position of the spore-wall is not known, but it is assumed 

 to be protein in nature. During germination it usually soft- 

 ens or gelatinizes, and in some cases becomes thicker at the 

 poles (Pig. 14 c). 



The contents of the spore, as seen from the method of 

 formation, are essentially those of the parent cell, less 

 water. Consequently the spore substance, which may be 

 considered as condensed protoplasm, contains all the pro- 

 teins of the original cell. Inasmuch as the bacterial cell 

 contains more or less fat it follows that the spore will like- 

 wise possess fatty compounds. The bright, highly refrac- 

 tive appearance of the spore is highly suggestive of the 

 presence of an oil-like body. When spores are treated with 

 ether no fat can be extracted, but this does not justify the 

 assumption that fat is absent. When ether is shaken up 

 with milk it will not remove the fat which is present in the 

 milk globules. 



Spores are, as a rule, perfectly colorless. In a few 

 fluorescing bacteria red spores have been observed. In 

 several other instances markedly green spores have been 

 met with. 



The anilin dyes do not stain spores as readily as the 

 vegetative form. This is commonly believed to be due to the 

 dense spore-wall, which hinders the penetration of the dye. 

 Undoubtedly, the contents of the spore will take up the 

 stain very slowly owing to the almost total absence of 

 water. For th e same reason, the contents, when once stained, 

 can be decolored only with difiiculty. The method of 

 double staining spores will be described in Chapter X. 



Spores are characterized by their extreme resistance to 

 destruction. The vegetating form is readily killed by mere 

 desiccation, whereas the spore can be kept in the dry con- 

 dition for years. Again, the vegetating form is killed in a 



