VIII REJUVENESCENCE OF MICROORGANISMS 281 



the host individuals for their rejuvenation. Some individuals peculi- 

 arly susceptible to a certain kind of bacteria may be infected and 

 utilized by them to establish the inheritance of their pattern to the 

 offspring of the host, in which bacteria will subsequently develop and 

 the offspring will be infected or become the bacterial carrier. 



As in the case of viruses, the susceptibility of the host may vary 

 with the regions where the host resides, leading to the establishment 

 of endemic diseases. Namely, in a certain region there may live 

 animals or man possessing extremely high susceptibility to a certain 

 kind of bacteria, which the latter therefore can continue their existence 

 particularly in such a region. In India cholera is almost always 

 prevalent. The true home of cholera is said to be the delta of the 

 Ganges. It spreads occasionally widely from this area, but in other 

 areas it usually dies out, though it may be reimplanted from time to 

 time. This may be accounted for by the non-existence, in areas other 

 than India, of hosts in which the bacteria can harbour. 



In addition to bacteria, a kind of yeasts {Schizosaccharomycetes 

 filtrans) and of protozoa {Trypanosoma Brucei) are known to- become 

 filtrable at a period of their life-cycle. Moreover, spirochaetes have 

 been reported to be able to exist in filtrable forms. According to 

 Nicolle (98), spirochaetes go into a filtrable granular stage produced 

 by fragmentation of the adult forms, and in the cycle of spirochaetal 

 development a phase seems to occur in which the organism persists 

 in the form of small granules. He considered that this form is ap- 

 parently resistant and latent, becoming infective when it regenerates 

 spirochaetes. Syphilis is caused by a kind of spirochaetes, Treponema 

 pallidum. It is a well known fact that the disease is transmitted 

 from parent to infant ; it should be noted that some authors believe 

 that the transmission is established not only by mother but also by 

 father. Numberous viruses have been confirmed to be transmitted 

 through germ cells of the host, but in the majority of cases only egg 

 cells are believed to be involved. Nevertheless, in the case of mam- 

 mary cancer of mice, which is generally recognized as caused by a 

 virus, it has been well established that males of cancer strains of 

 mice may transfer the agent through the sperm (99) (100). Treponema 

 pallidum may be transmitted in a similar way to the offspring. 



As stated already, fungi in the insect are undoubtedly transferred 

 through eggs from generation to generation, whereas many grass 

 smuts are known to be seed-born ; that is, the pathogenic fungi are 

 carried by the seeds to progeny (101). The mechanical transport of 

 the fungous spores by seeds may not be an adequate explanation of 

 this fact. 



It is worthy of note that in the gut of the termite, protozoa occur 



