GONADS AND THE PITUITx^RY BODY 



I0-20 days and total doses are doubled or quadrupled (Fluh- 

 mann, 1933). Not much success has attended efforts to refine 

 the quantitative assay of gonadotropic hormone by using the 

 hypertrophy of the immature rat's ovary as a criterion. Doses 

 differing in amount by more than 50 per cent possibly can be 

 distinguished if twenty rats are used in a group and condi- 

 tions are rigidly standardized (van Dyke and Wallen-Law- 

 rence, 1933)/'' Using doses, in part large enough to produce 

 ovaries weighing more than 100 mg., Hill, Parkes, and White 

 (1934) also were not able to demonstrate a satisfactory rela- 

 tionship between the dose of an anterior-pituitary extract and 

 the ovarian weight. In experiments in adult mice, however, 

 they obtained more consistent results. 



In adult rats the injection of an anterior-pituitary extract 

 may cause considerable or even marked luteinization of the 

 ovary in which corpora lutea atretica are formed; the oes- 

 trous cycles consequently become irregular and lengthened, 

 or disappear (Evans and Long). The luteinizing potency of 

 an extract can be determined roughly by its effect on the 

 length of the oestrous cycle of a group of rats; there is a fairly 

 satisfactory relationship between the dose of a prepara- 

 tion and the consequent lengthening of the oestrous cycle 

 (D' Amour and van Dyke, 1933). Lipschiitz estimated the 

 amount of luteal tissue by determining the weight of the 

 ovary and the percentage volume of luteal tissue in serial 

 microscopic sections of the ovary. He recommended that the 

 luteinizing effect of an extract or implants on the ovary of the 

 immature rat be stated as the quotient 



mg. lutein tissue 



mg. anterior-lobe implant (or extract) 



The weight of a "unit" of anterior-pituitary gonadotropic 

 extract assayed in the immature or adult mouse appears to be 

 |-i of the weight of a unit assayed in the immature rat. 



^' In the experiments of van Dyke and Wallen-Lawrence another preparation, 

 the dose of which was not varied, had to be given for comparison. 



[173] 



