425 V. THE NATURE OF EVOLUTION 



long before any specific immunization or therapeutic m.easures were 

 available. 



The writer claims that these two amazing phenomena are closely 

 related with each other. As mentioned above, adrenal cortex is 

 controlled by hypophysis, and environmental factor stimulating the 

 anterior pituitary gland causes the secretion of adrenocorticotrophic 

 hormone, which in turn induces the secretion of cortex hormone, 

 whereas the same factor leads to the involution of thymus and other 

 lymphatic organs. On the other hand, as is well known the so-called 

 "status thymicolymphaticus" is a status liable to be affected by pulmo- 

 nary tuberculosis. Its characteristics are an excessive development of 

 the thymus, tonsils and other Ij^mphatic organs, with a concomitant 

 hypoplasia of the adrenal cortex. Moreover, intimate relation between 

 tuberculosis and Addisonism, known as a morbid state associated 

 with a dysfunction of adrenal cortex, has also been generally accepted. 

 It can be concluded, therefore, that the hyperfunction of hypophysis 

 caused by hypophysis-stimulating environment may result in the in- 

 crease in the growth-hormone secretion, thereby man obtains a 

 gigantic figure, and at the same time, it may remove the status 

 thymicolymphaticus and Addisonism, thus rendering man insensitive 

 to tuberculosis. 



The average span of man's life is said to have been lengthened 

 steadily during the same time in civilized nations. This must be 

 a natural result of the increase in man's stature, since in general 

 the bigger the animal, the longer its life. On the contrary, the 

 hyperfunction of thyroid gland, which seems to be antagonistic to 

 the action of adrenocorticotrophic hormone and which may be brought 

 about by the want of the stimulating factor may result in the 

 shortening of life span because of the premature growth due to the 

 hormone. 



It is little doubt that the remarkable morphological change in 

 man, above mentioned, has begun to occur comparatively recently. 

 According to Schwidetzky (106) as illustrated in Table 11, the head 

 form of man has shown a great change at least after the year 1200 ; 

 it should be noticed that almost no significant change occurred during 

 the period ranging from 1200 B. C. to 1200 A. D. Moreover, it is 

 reported that the actual increase in the stature in a generation among 

 Yale University students has been about IV2 inches (103). If man 

 had continued in the past to become bigger at this rate, only 1,000 

 years ago he would have been a dwarf of only about 2 feet ; such 

 was of course never the case. It is evident, therefore, that the 

 change began recently and is continuing to proceed with a frightlful 

 speed. Of course, the period of time extending over only a few 



