XII. THE EVOLUTION OF MANKIND AND ITS FUTURE 435 



On the view point of easy infection, the increase in the number of 

 children must result in the increase in the incidence ; this is shown 

 when the number is less than three, but the reverse is the case 

 when the number is greater than three, showing the overwhelming 

 influence of another factor acting in the reverse direction. This re- 

 minds us of the fact, already shown in Fig. 39, which indicates that the 

 stature of the children is the taller, the fewer their number in a family. 

 Thus there is little doubt that the easy going life of children of small- 

 sized family increases in them the sensitivity to whooping-cough as in 

 more civilized nation. 



It has been confirmed by us (133) that the incidence of measles and 

 whooping-cough in Kanagawa Prefecture in Japan was reduced remark- 

 ably at the end of, or immediately after, the War ; this fact indicates 

 that the uneasy life of the children at the end of the War bears a 

 striking resemblance to the usual but irritable, and food-insufficient 

 life of the children of a large family. In addition, it is generally 

 accepted that also intestinal toxic disorders of children and appendicitis 

 almost entirely ceased to occur in Japan during the War. Even com- 

 mon bacterial infectious diseases such as dysentery and typhoid fever 

 were said to have been likewise remarkably diminished. The develop- 

 ment of the pattern of causative agents of these diseases, whether 

 they were viruses or bacteria appeared thus to have been inhibited by 

 the same factors. As is generally accepted, tuberculosis, on the 

 contrary, increases strikingly during wars, a phenomenon most probably 

 due to the want of nutrition which causes a hormonal unbalance 

 including the dysfunction of adrenal cortex favouring the disease. 



It is needless to mention that inanition is generally accepted to have 

 an intimate connection with tuberculosis. However, if one considers 

 that inanition causes a general decrease in the resistance to infectious 

 diseases he commits a great mistake, because it is well established 

 that an ill-fed animal is less susceptible to virus diseases including 

 cancer than a well-fed one, as is readily expected from the theory 

 above stated. 



One of the earliest demonstrations of this phenomenon was that of 

 Rous (134), who in his experiments on fowl sarcoma virus, emphasized 

 that healthy, well nourished fowls were more susceptible to the virus 

 than the thin and ill. Olitzky, et al. (135) found that guinea pigs 

 suffering from malnutrition were resistant to infection upon inocula- 

 tion with the virus of foot-and-mouth disease than were normal, 

 healthy animals. Recent reports dealing with nutrition and poliomye- 

 litis have contribute further data on the way in which nutritional 

 deficiency can decrease susceptibility. It is a note-worthy fact that 

 cancers are very difficult to transplant in otherwise susceptible animals, 



