THE PITUITARY BODY 



It is important to emphasize that "units" assayed by these 

 various techniques are not necessarily interchangeable or re- 

 lated to each other. In every case the assay is based on a 

 "gonad-stimulating" efFect.^^ Too frequently in assays, im- 

 portant factors influencing the type or degree of response 

 elicited are neglected. Among these may be mentioned age, 

 race, and nutritional condition of the animals, season or 

 other factors (as in the use of rabbits), route of administra- 

 tion, distribution and frequency of doses, and the use of a 

 sufficiently large group of animals (twenty or more) receiving 

 an amount of hormone producing changes in only part of 

 the group. 



Particularly in immature female mice and rats does assay 

 by indirect methods appear to be undesirable and incom- 

 plete. When these have been compared with the direct ef- 

 fects — e.g., luteinization — the relationship has appeared to be 

 the same to some or variable to others. A priori it would seem 

 to add an unnecessary and complicating variable. On the other 

 hand, the assay of prolan in male immature mice and rats 

 by noting indirect effects appears to be a more sensitive and 

 exact method because only a relatively small part (inter- 

 stitial cells) of the total testicular tissue is affected by prolan. 

 Variable changes in testicular weight are produced only by 

 large doses of prolan. 



The assay of prolan in immature female mice and rats. — 

 The relative sensitivity of mice and rats has already been 

 discussed (see pp. 186-87). The use of rats in preference to 

 mice appears to have the following advantages: rats produce 

 larger litters, are better standardized, are more sensitive to 

 the hormone, but are less easily poisoned by substances acci- 

 dentally present. In rats, assay may be based either on the 

 frequency of qualitative changes such as follicular growth 



^9 Some authors assert that melanophore changes (dispersion of melanosomes) 

 in fish scales and frog skin can be used for the assay of prolan (Binet, Verne, and 

 Luxembourg, 1934, Konsuloff, 1934). 



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