GROWTH AND THE AGING PROCESS 



967 



and invertebrate forms the life span is prolonged by extension of the growth period. 

 Since that time a number of investigators have shown that in many different zoolog- 

 ical forms a diminution in food intake increases longevity. Thus Rudzinska (1951) 

 has shown this to be true for Protozoa; Tannenbaum (1947) for mice; and Carlson 







,'^^ 



*►> # /. 



Fig. 8A. Thyroid gland of a young mouse, a 213-day female. There is litde connective 



tissue between the follicles. The epithelium is of simple cuboidal type, x 427. 



Fig. 8B. Thyroid gland of a senile mouse, an 811-day female. The epithelium in many 



follicles is flattened and atrophic, while the colloid appears very dense. Fibrous connective 



tissue is abundant. X 427. (Figs. 8A and 8B after Andrew, 1956). 



Literature p. 971 



