252 CHARLES E. STOCKARD 



tomal enlai'gements would be expected; following this period 

 there is a decided fall in growth rate and the teratomata of early 

 childhood may occur. The alternating periods of fast and slow 

 growth should then "continue to correspond with periods of few 

 and many recorded teratomata. Dr. H. E. Himwich has under- 

 taken a careful survey of the teratomata as recorded in the lit- 

 erature in order to ascertain whether any apparent relationship 

 does exist between the time of occurrence of a teratoma and the 

 periods of fast and slow growth rate in man. The results of his 

 investigation are soon to be published. 



12. CANCEROUS GROWTHS AND THE GENERAL CESSATION OF ALL 

 NORMAL GROWTH IN THE OLD INDIVIDUAL 



In an interpretation of the cause of cancer the fact that the 

 condition is so much more frequent in the adult and old individ- 

 ual than in the young is to be recognized as of deep significance. 

 The fact that there is an interaction and especially a growth- 

 inhibiting effect exerted among proliferating tissues in the indi- 

 vidual is a second point of great importance. 



In the young rapidly growing and developing person almost 

 all organs and tissues are increasing in amount through multi- 

 plication of their cellular constituents. The liver, for example, 

 grows in actual mass until it reaches the adult size. This size, 

 although decidedly variable in a group of individuals, has rather 

 definite limits. The normal human liver is never indefinite or 

 unlimited in its growth. Almost all other organs are similarly 

 of limited size. Thus growth in general tends to cease as the 

 body approaches its adult proportions. Finally, in the old indi- 

 vidual, the only remaining cell proliferation becomes almost 

 entirely confined to the germinative layer of the skin, the lining 

 epithelium of the alimentary tract, the testes in the male, and 

 the production of red blood-corpuscles. Even these proliferation 

 processes become feeble with increase in age and new cells are 

 not abundantly supplied. This is the normal course of events. 



The size and proportion of parts are largely determined by 

 heredity, but may be seriously interfered with by irregularities 

 in the environment. 



