OVARY AND THE ANTERIOR PITUITARY BODY 171 



ruptured follicle into luteal tissue. If one substance only is 

 involved, quantitative variation probably produces the different 

 effects. 



It has been shown by Engle (178) that the hypertrophy of the 

 remaining ovary after unilateral ovariectomy is greatly 

 expedited by the injection of anterior pituitary substance. The 

 author considers this result as evidence that the factor limiting 

 the number of follicles ovulated at any one time, the factor 

 governing the law of follicular constancy, variously called 

 'generative ferment' or X-substance, is merely the follicle- 

 stimulating principle of the anterior pituitary. 



Influence of changes in the accessory organs on the anterior 

 pituitary. It is necessary to mention here some theoretical 

 considerations upon which no work has been carried out. If 

 the anterior pituitary is directly responsible for the changes in 

 the ovary, then some means must exist whereby events in the 

 accessory organs can influence the anterior pituitary. For 

 instance, since ovulation does not take place during pregnancy, 

 some mechanism must cause the anterior pituitary at this time 

 to stimulate the corpus luteum and not the follicle. Similarly, 

 it must be concluded that the absence of oestrus during pseudo- 

 pregnancy in the mouse indicates that the anterior pituitary 

 body reacts to sterile copulation and exerts a stimulating 

 effect upon the corpora lutea. Since the effect of sterile 

 copulation can be produced by mechanical irritation of the 

 uterine cervix, it would seem that such stimulation can react 

 upon the anterior pituitary. 



A similar conclusion is reached by another argument. The 

 fact that cervical stimulation will activate the corpora lutea in 

 a grafted ovary in the rat (425) makes it fairly certain that the 

 effect is not direct. The intermediate point, where the stimulus 

 changes from nervous to endocrine, may reasonably be supposed 

 to be the anterior pituitary. In the rabbit copulation probably 

 causes ovulation (see p. 54) by stimulation of the anterior 

 pituitary. Since the action of copulation can only be nervous 

 in nature, ovulation in the rabbit would appear to occur as the 

 result of a vulva-pituitary-ovary chain of stimulation, in which 

 the first link is nervous and the second endocrine. 



Similarly, the fact that lactation in the rat and mouse 



