130 INTERNAL SECRETIONS OF THE OVARY 



opossum is very obvious and can actually be detected b}^ 

 palpation of the intact animal. Allen (12) also has described 

 hypertrophy of the mammae in Macacus rhesus after the 

 injection of cestrin, while Loeb (405) has dealt with the same 

 effect in the guinea-pig. Laqueur and co-workers (351) have 

 recently, by injecting oestrin, produced hypertrophy of the 

 mammae in normal and ovariectomized female, and normal 

 and castrated male guinea-pigs, in young male dogs, and in 

 castrated monkeys. They consider oestrin to be the normal 

 stimulus for the entire development of the mammary gland. 

 Haterius (283) obtained hypertrophy of the mammary tissue of 

 male guinea-pigs by the same treatment. Similar results on the 

 ovariectomized guinea-pig have been reported by Steinach and 

 co-workers (593). 



Superficially, all this would appear to be evidence against the 

 great mass of observational and experimental data which seems 

 to show that the corpus luteum is responsible for the develop- 

 ment of the mammary gland. Actually, however, it is highly 

 probable that no such interpretation can be placed upon these 

 results. In the first place, few workers claim to have produced 

 sufficient development in the mammary gland to lead to the 

 secretion of milk. Fellner (192) specifically states that the 

 growth was not enough to allow of milk secretion. It seems 

 most probable that the degree of development of the mammary 

 gland which can be produced by the injection of oestrin is only 

 comparable to that which has been shown to occur normally 

 at oestrus in many species and to be quite independent of the 

 main development during pregnancy, which is under the control 

 of the corpus luteum. In Chapter III it was pointed out 

 that a cycle in the mammary gland in the unmated animal may 

 be just as typical of the oestrous cycle as is the cycle in the 

 uterus and the vagina. Thus, in the guinea-pig Loeb and 

 Hesselberg (402) have shown that proliferation in the mammary 

 gland occurs at oestrus, while Myers (472) has described cyclic 

 mammary changes in the non-pregnant rat. Marshall (444) 

 describes hyperplasia of the mammary gland in the mare at 

 oestrus. Hartman (271) in discussing the oestrus cycle in the 

 opossum also emphasizes the fact that the amount of growth in 

 the mammary gland at the time of oestrus, although consider- 



