OVARY AND THE ANTERIOR PITUITARY BODY 163 



rarely find any atretic follicles in the precociously matured 

 animals.' According to Eels (206) the formation of atretic cor- 

 pora lutea is more frequent than ovulation. In view of the earlier 

 work of Evans on the luteinizing effects of anterior pituitary 

 this distinction is of considerable interest. The problem of 

 whether one or two anterior pituitary substances are involved 

 is discussed below. 



The pioneer work of Zondek and Aschheim, and of Smith and 

 Engle has now been confirmed- by many authors, including Eels 

 (206), Brouha and Simonnet (100), Loewe and co-workers (423) 

 and Siegmund (564). Brouha and Simonnet, however, consider 

 that another pituitary substance, fat-soluble and producing 

 oestrus in castrated animals, can be demonstrated. 



{d) ARE TWO ANTERIOR PITUITARY SUBSTANCES 

 CONCERNED IN THE REGULATION OF THE OVARY? 



The difference in the effects following injection of Evans' 

 sodium hydroxide extract and injection of the macerated fresh 

 tissue, led to the tentative supposition that two different 

 anterior pituitary principles were involved, one causing the 

 conversion of the follicular granulosa to luteal cells and another 

 causing the burst of growth preceding follicular maturation. 

 Doubt has recently fallen on this supposition. In the first 

 place, the method of obtaining the two preparations is funda- 

 mentally different, {a) The macerated suspensions are fresh and 

 correspond only to minute amounts, 5 to 20 mgms., of fresh 

 tissue daily; the sodium hydroxide extracts, on the other hand, 

 made from ox pituitaries, may not be really fresh and the daily 

 amount injected corresponds to about i gm. of original tissue. 

 (b) The later preparations used by Evans (182) were subjected to 

 a fairly drastic chemical treatment, namely, extraction with 

 sodium hydroxide. His earlier extracts, however, were only 

 made with saline; and similar suppression of ovulation has 

 been obtained by Walker (629) who administered the fresh 

 substance to fowls. 



More serious criticism of the view that two anterior pituitary 

 substances are involved is forthcoming from the work of Zondek 

 and Aschheim (656). These authors, in investigating the effects 



