SPORES 35 



end of the cell either without (Fig. 32) or with enlarging it 

 (Fig. 33). In a few forms the spore is placed at the end of 

 the rod and shows a marked enlargement. This is spoken 

 of as the " plectridium," or more commonly the "drumstick 

 spore" (Fig. 34). The position and shape of the spore are 

 constant for each kind of bacteria. In one or two instances 

 only two spores have been observed in a single organism. 



The fact that the protoplasm is denser and the spore cap- 

 sule thicker (the percentage of water in each is decidedly 

 less than in the growing cell) gives the spore the property 

 of much greater resistance to all destructive agencies than 

 the active bacterium has. For example, all actively growing 

 cells are destroyed by boiling in a very few minutes, while 

 some spores require several hours' boiling. The same rela- 

 tion holds with regard to drying, the action of chemicals, 

 light, etc. That the coagulation temperature of a protein 

 varies inversely with the amount of water it contains is 

 shown by the following table from Frost and McCampbell, 

 General Bacteriology. 



Egg albumen plus 50 per cent water coagulates at 56° 



" 25 per cent " " " 74-80° 



" 18 per cent " " " 88-90° 



" 6 per cent " " " 145° 



dry " " " 160-170° 



This resistance explains why it happens that food materials 

 boiled and sealed in cans to prevent the entrance of organ- 

 isms sometimes spoil. The spores have not been killed by 

 the boiling. It explains also in part the persistence of some 

 diseases like anthrax and black leg in pastures for years. 

 From the above description it follows that the spore is to 

 be considered as a condensation of the bacterial protoplasm 

 surrounded by an especially thick cell wall. Its function is 

 the preservation of the organism under adverse conditions. It 

 corresponds most closely to the encystment of certain 

 protozoa— the ameba for example. Possibly the spore 

 represents a very rudimentary beginning of a reproductive 

 function such as is gradually evolved in the higher thread 

 bacteria, the fission yeasts, the yeasts, the molds, etc. 



