THE GROWTH-PROMOTING HORMONE 



Other experiments have been performed in hypophysec- 

 tomized dogs. The daily injection of the hormone for weeks 

 may correct the majority of the growth- defects without caus- 

 ing the changes described above. Growth may be as rapid or 

 more rapid in comparison with httermate normal animals. 

 The first dentition instead of persisting is replaced by the 

 second dentition at about the normal time. The epiphyses 

 close only a short time later than those of normal young dogs. 



The effects of growth-promoting extract in growing normal 

 mice appear to resemble those in normal rats. Johnson and 

 Hill (1930) believed that the female mouse responded better 

 than the male, although their data were hardly numerous 

 enough to justify such a conclusion. The mice of Smith and 

 MacDowell (1930-31) were dwarfs because of a hereditary 

 defect of the pars glandularis. If they were given implants of 

 fresh pituitary from normal rats or mice they grew to resem- 

 ble normal mice. Kemp (1934) administered the growth-pro- 

 moting hormone to similar dwarf mice. The gonads were not 

 normal, but normal growth took place in the body and its 

 other parts with the exception of the thymus, which was 

 markedly hyperplastic. According to Downs (1930), the in- 

 cisor of the normal mouse erupts more rapidly if growth- 

 promoting extract is administered. 



Engelbach and his colleagues (1932-34) have described in- 

 creases in the weight, increases in the height and other dimen- 

 sions of the body, and changes in the roentgenograms of 

 bones and joints after the administration of the growth-pro- 

 moting hormone (often combined with thyroid extract) to 

 dwarfed human beings. 



SPECIAL CONSIDERATIONS 



The specificity of the efiects. — Growth-promoting effects — 

 in the sense in which they have been described in the preced- 

 ing pages — are obtained only by the administration of tissue 

 or extracts of the pars glandularis of the pituitary body. The 



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