THE PITUITARY BODY 



which the weights of two male rats — one injected and one 

 normal — are plotted against time, which in this instance 

 amounted to more than 20 months. 



Unless large doses of growth-promoting extract are em- 

 ployed, the differences between normal and injected growing 

 rats are not striking until after the age of 75-100 days. 

 Thereafter, normal rats grow slowly, whereas those receiving 

 suitable doses of the hormone continue to increase in weight 

 at a rapid rate so that at ages of 200-400 days the injected 

 rats may be twice as heavy as normal rats — surpassing in size 

 normal rats of any age (Evans, 1924). The important change 

 in such experimental gigantism is in the weight, although the 

 size of the body and its parts, including the skeleton,^ is in- 

 creased. As in human acromegaly, the viscera are enlarged. 

 The belief of Evans and Long that an important part of the 

 weight increase is due to the deposition of fat has not been 

 confirmed by others (see below, pp. 100-102). 



Crude extracts of the pars glandularis also produce changes 

 in the gonads. The discussion of the gonadotropic effects of 

 such extracts, however, will be taken up in chapter iv. 



The administration of growth-promoting extracts to rats 

 which are otherwise normal produces a greater relative 

 change in the weight and size of the female rat (Johnson and 

 Sayles, 1929; Evans and Simpson, 1931; Simon and Binder, 

 1932; and Rubinstein and Kolodner, 1934). In terms of the 

 absolute weight and size, however, the largest rats produced 

 by the repeated injection of the hormone are males. If the 

 administration of the growth-promoting extract is delayed 

 until the rats are growing very slowly, and if the period of ad- 



s Handelsman and Gordon (1930) concluded that normal periosteal bone-growth 

 was stimulated by the growth-promoting hormone but that this effect could not be 

 clearly shown except in animals approaching adult weight. Lucke and Hiickel 

 (1933) observed proliferative changes in the joint cartilage as well as both prolifera- 

 tive and retrogressive changes in the epiphysial cartilage, all of which they attribut- 

 ed to the administration of a growth-promoting extract. They concluded that the 

 alterations resembled those accompanying the specific arthritis of early human 

 acromegaly. 



[88] 



