NATURAL AND ACQUIRED IMMUNITY 103 



scarlet fever at birth and a ratio of 1 to 45 among adults. Scarlet 

 fever is said to be unknown among the Eskimos, and it is interest- 

 ing to note that Heinbecker and Irvine- Jones (1928) found no 

 positive reactors to scarlatinae toxin among 53 Eskimos tested by 

 them. These investigations seem to offer examples of racial im- 

 munity to diphtheria and scarlet fever respectively. There is a 

 great deal of controversy over tlie interpretation of the results and 

 more than one explanation of the phenomena. 



Wells* (1933) made an extensive study of tlie bacterial flora 

 of the tliroat of a fairly large series of Eskimos. He noted the 

 presence of nonvirulent corynebacteria quite frequently in throat 

 cultures. In one instance a transient virulence was observed. 

 From his serological, epidemiological and bacteriological studies 

 he feels warranted in concluding that the immunity to diphtheria 

 observed among the Eskimos ''is specific rather than the result of 

 maturation phenomena." He admits, however, that his evidence 

 is not conclusive. 



Endocrines AND IMMUNITY. — There is a growing interest in de- 

 velopmental physiology and anatomy. Research in these fields may 

 ultimately result in a better understanding of the defensive 

 mechanisms of the individual at different periods in his life cycle. 

 Scammon (1925) and others have carried out extensive work in 

 developmental anatomy. They have worked out interesting growth 

 curves but have not studied the corresponding cellular and bio- 

 chemical changes. 



Recent work suggests that the suprarenal cortex regulates, by its 

 secretions, the permeability of vessel walls. In other Avords this 

 secretion determines what substances stay witliin tlie walls and 

 what escape into the tissues. When one turns to the develop- 

 mental curve for the suprarenals, it is interesting to note that 

 Scammon (1925) and others have shown that the suprarenals in- 

 crease rapidly during fetal life, weighing about 7 grams at birth. 

 During the first two years of postnatal life they undergo a rapid 

 diminution in size to about a third of the natal weight. This re- 

 duction in weight is due to an involution of the middle and inner 

 cortical zones. From about tlie second year they gain very slowly 

 in weight until middle or later childhood when accelerated growth 

 is noted for a period and then a gradual growth until maturity. 



•Wells. J. R. : Am. J. Hyg. 18: 629, 1933. 



