THE ENDOCRINE SYSTEM 



207 



Gigantism is caused by an overstimulation of the growth of bones, 

 particularly the long bones, during childhood, before the epiphyses 

 (cartilaginous zones near the ends of the long bones) have 

 ossified. A recent authenticated example of gigantism is that 

 of a boy 19 years old, weighing 435 lb. and measuring 8 ft., 

 6 in. in height and still growing. Acromegaly also involves bone 

 development, but since it arises in adult life, after the length 

 of the bones has been fixed, the result is an increase in breadth 

 of the bones, particularly noticeable in the bones of the face, 

 hands, and feet. In both gigantism and acromegaly, post- 

 mortem examinations show hypertrophy (enlargement) of the 



Fig. 131. — Cut surface of right half of pituitary gland and floor of diencephalon 

 of rat, semi-diagrammatic, a, anterior lobe; i, intermediate lobe; i.s., infundibu- 

 lar stalk; p, posterior lobe; 3, third ventricle. {From a preparation by L. B. 

 Hobson.) 



anterior pituitary lobe. Gigantic rats and acromegalic dogs have 

 been produced experimentally by the injection of extracts of the 

 anterior pituitary lobe. 



Go?iadotropic Hormone. — One of the results of removing the 

 anterior pituitary lobe of young mammals is the suppression of 

 gonad development. Conversely, implantation of anterior lobe 

 tissue under the skin or in the muscle of young rats causes a 

 precocious development of the gonads. The ovary of the frog, 

 Rana pipiens, is quiescent and does not produce mature eggs 

 except during the breeding season, which occurs in the spring. 

 However, ovulation can be induced at other times by implanting 

 fresh frog pituitary tissue. As a result mature eggs may be 

 obtained in the middle of winter. The testes of the male may 

 be stimulated to produce mature spermatozoa by similar treat- 

 ment. In fact, all the sexual responses, including amplexus, may 



