GONADS AND THE PITUITARY BODY 



out that the response is less if the rabbits have already been 

 used three times (at intervals of 3 weeks). They define 

 their "unit" as the amount of extract (given intravenously to 

 each rabbit) causing ovulation in 50 per cent of a group of at 

 least 10 rabbits. If a standardization curve is to be em- 

 ployed it probably should be first determined by the use of 

 larger groups (20-30). 



4. The stimulation of the growth of follicles and /or the forma- 

 tion of corpora lute a in immature or adult mice and rats. — 

 Both the qualitative and the quantitative assay of gonado- 

 tropic hormones in immature mice and rats have been under- 

 taken by many investigators. For qualitative effects, oestrus 

 (including uterine changes), follicular growth, follicular ma- 

 turation, ovulation, and corpus luteum formation have been 

 studied. Quantitative studies have been concerned mainly 

 with the changes in the weight of the ovaries. For the assay 

 of most gonadotropic extracts, the determination only of the 

 change in the weight of the ovaries must be considered un- 

 satisfactory if one is to bear in mind the possibility or proba- 

 bility of the existence of several anterior-lobe gonadotropic 

 hormones. Such a quantitative change (increase in ovarian 

 weight) may not be related to the qualitative change. The 

 qualitative changes probably are interrelated in a complex 

 way not only among themselves but also with the adminis- 

 tered extract. The difficulty of analysis is further increased 

 by the presence of the test animal's own pituitary^^ — usually 

 an unknown factor in the response. Nearly all the data from 

 which conclusions are drawn as to the presence of several 

 gonadotropic hormones in the pituitary were obtained in ani- 

 mals with the pituitary intact. 



Other factors in the response of the ovary of immature 

 mice and rats to gonadotropic hormone(s) are diet, age, and 

 weight. Ordinary assays probably should not be started in 



''■'For example, see Swezy (1933-34); Hohlweg (1934); and Selye and others 

 (1935)- 



[171] 



