V. GRADUAL ALTERATION OF GENE 



377 



« 5 2 

 S5 =« 



60 O 





-J — 



f 2 3 ¥ 5 S 



Time in hours. 



Fig. 35. The progress of the Inactivation of phage protein due to 

 formaldehyde. Concentration of formaldehyde 0,05% (I) and 0,1% 

 (II). Concentration of phage protein: 0,05%: pH = 7,5. 



presence of a factor or factors making the change leading to senescence 

 proceed continuously. As already discussed, senescence is a pheno- 

 menon occurring when the proteins or organisms continue to exist 

 under the same environmental condition. Proteins having biological 

 actions, such as toxins, antibodies, or enzymes, will achieve a gradual 

 change, known as denaturation, when preserved in vitro after being 

 separated from organisms. The change is usually very gradual and 

 frequently many years may elapse before complete inactivation occurs. 

 Such a change is likewise attributable to the continued presence of 

 some factors which cause the denaturation. Furthermore, the pro- 

 duction of cancer from a somatic cell as w^ell as the development of 

 adult from a germ cell is considered to be brought about by a con- 

 stant influence of a series of proper stimuli as already discussed. 



Here again, we have to consider the problem of reversibility. It 

 is true that sometimes formalin-inactivated phage is reactivated 

 following the removal of formalin, but the reactivation occurs only 

 seldom, usually being irreversible. The same can be said with phage 

 inactivated by chemical or physical factors other than formalin. How- 

 ever, the reduction of the virulence of phage, without inactivation, 

 due to extremely small amounts of formalin is usually reversible (60). 

 Namely, the virus reduced in its virulence by formalin may produce 

 small plaques on agar plate, but after a period of incubation following 

 the removal of formalin the original property to produce plaques of 

 ordinary size will generally be recovered. Such a reversible change 

 •can be demonstrated not only with formalin, but also with such 

 agents as antibody, mercuric chloride, and tannin '61) (62). In general 



