VIII REJUVENESCENCE OF MICROORGANISMS 277 



virus. The manner of establishment of the infection seems likewise 

 very similar to that of measles ; new born babies are scarcely infected, 

 but the incidence increases rapidly with their growth until almost 

 all of them are affected. This fact is usually explained to be due to 

 the increase in the chance of infection as infants grow older, whereas 

 it may also be possible to regard this as analogous to the phenomenon 

 already discussed that larvae hatched from eggs of insects which 

 were infected by a certain plant virus produce no virus when very 

 young, but that as grow older they become infectious. As we shall 

 see in the following, there are many good reasons to consider this 

 interpretation to be much more reasonable than the former. 



The concept that the tuberculosis is produced only by the infection 

 from outside may be confused by the so-called Liibeck tragedy, in 

 which 251 new born infants instead of the avirulent bovine bacillus 

 BCG, a living human virulent strain was accidentally substituted in 

 the laboratory. The bacilli were given by mouth in so large an 

 amount as 400,000,000 microorganisms, on three different occasions 

 during the first ten days of life, with the result that 75 of them dead 

 and 175 w-ere living, eacaped death or even progressive tuberculosis. 

 Moveover, in a study of children in tuberculous families. Puffer (87) 

 has shown that of the contacts with sputum-positive parents infection 

 came earlier than those of sputum-negative parents, but, by the time 

 to come of ages of fifty, contact and non-contact cases with positive 

 heredity showed the same percentage of infection. 



According to Pottenger (88), the fact that the apex is not particu- 

 larly susceptible in first infection, which so commonly takes place in 

 childhood, but shows a particular predilection for reinfection in the 

 adult, indicates that something occurs in the time between childhood 

 and adult life which changes the localization of the bacilli ; he stated 

 that it might further indicate that the source of the bacilli and the 

 route of invasion might be different. Such a phenomenon should be 

 only natural if the bacilli are produced in human bodies. 



For a long time it was known that tubercle bacillus can exist in 

 a virus-like filtrable form, and numerous workers have claimed that 

 this filtrable form constitutes a special stage in the life-cycle of the 

 bacillus. This fact strongly supports the above concept, since, if the 

 bacillus is transmitted by human germ cells, it should be reduced, at 

 least during the transmission, into the form of a virus, from which 

 subsequently bacillary form develops. Moreover, tubercle bacillus is 

 known to be one of the acid-fast bacteria, but in young cultures it is 

 common to find a certain proportion of non-acid-fast forms. In view 

 of these facts numerous workers believe that the life-cycle of the 

 bacillus consists in that the virus-like particles develop into acid-fast 



