44 MORPHOLOGY OF BACTERIA 



Others consider there to be a relationship between the richness of 

 the cell in granules and its virulence. Hill, however, considers that, 

 inasmuch as nitrates increase the nitrogen assimilated by Azotobacter 

 and the number and size of the volutin bodies, they bear some 

 relationship to the organisms' power to fix nitrogen. Although it 



FIG. 12. Successive stages in division of Bacillus diphtherice, showing relation of 

 line of division to metachromatic granule. Continuous observation of living bacillus 

 drawn without camera lucida. (Williams.) 



is quite possible that they may possess various functions in differ- 

 ent organisms, the majority of them would seem to be, as suggested 

 by Mev_pr, reserve food materials which occur in the cytoplasm of 

 the cells of various bacteria. They are most numerous in rapidly 

 growing young cultures and usually disappear when the food becomes 

 scarce. 



FIG. 1 3. Types of bacterial spores. (Kendall.) 



Spores. Bacteria possess the power of mobilizing the vital parts 

 of their body into a much smaller space than they occupy during 

 their normal life. They exclude all of the excess moisture and sur- 

 round themselves by a tough resistant coat. In some respects 

 this form of the organism resembles the seed of the higher plant 

 and we speak of it as a spore. While in this stage they will with- 

 stand many conditions which would quickly prove fatal to growing 

 bacteria. Some of them can withstand the temperature of boiling 

 water for many hours, or they may survive treatment with strong 

 carbolic acid. For the time being they have lost the power of mul- 

 tiplying, but they are still alive and if they are brought into appro- 

 priate surroundings they will change back Into normal bacteria just 

 as a kernel of wheat changes into the young plant when placed in 

 moist soil. It is indeed fortunate for mankind that but few of the 

 disease-producing organisms form spores. There are, however, 

 many of the bacteria which cause fruit, meat, and various other 

 food products to spoil, which do form very resistant spores and this 



