THE PITUITARY BODY 



the gonads, thyroid, and adrenal cortex; whereas, crude ex- 

 tracts have no effect on these structures, but may even pre- 

 vent the beneficial effect of the implants on the gonads. 



Hypophysectomized rats respond more readily to the 

 growth-promoting hormone than do normal adult rats (van 

 Dyke and Wallen-Lawrence, 1930; Evans, Pencharz, Simp- 

 son, and Meyer, 1933). The aged normal rat may respond 

 poorly to the injection of a growth-promoting extract (Han- 

 delsman and Gordon, 1930). Similarly, van Dyke and Wal- 

 len-Lawrence found that hypophysectomized rats, 4 months 

 or more after operation, might be completely unresponsive to 

 doses of growth-promoting hormone causing a clear-cut in- 

 crease in the weight of other rats hypophysectomized more 

 recently. Such animals also might exhibit no weight increase 

 after nineteen homo-implants administered once daily. How- 

 ever, if the growth-promoting hormone was injected for a 

 longer period with no attempt to use doses near a threshold 

 level (for recently hypophysectomized rats), growth could be 

 stimulated in rats 294-336 days after hypophysectomy 

 (Schour and van Dyke, 1932). Similar results were obtained 

 by Evans and his co-workers (1933) in one rat given injec- 

 tions 279 days after operation as well as in four others first 

 treated 1 28-1 51 days after operation. 



The rate at which the incisor tooth of the rat erupts be- 

 comes markedly reduced as a result of hypophysectomy. A 

 growth-promoting extract increases the rate of eruption if an 

 associated general growth-response also occurs. The hormone 

 has no effect on the rate at which the incisor erupts in the 

 normal rat, although it causes an increase in the body-weight 

 (Schour and van Dyke, 1932). Putnam, Teel, and Benedict 

 (1928) reported that the hair grew more slowly after hypo- 

 physectomy but that this deficiency could be corrected by the 

 administration of a growth-promoting extract. Snow and 

 Whitehead (1935) made a careful study not only of the condi- 

 tion of the skin and hair of hypophysectomized rats, but also 



[90] 



