556 



Dr. F. H. A. Marshall and Mr. E. T. Hainan. 



degenerate after a shorter period. This statement is certainly correct for 

 some species, but the matter is one which requires extended study on com- 

 parative lines. 



The similarity between the developmental progress of the mammary tissue 

 occurring in the postoestrous non-pregnant Dog and that taking place under 

 experimental conditions in^ the pseudo-pregnant Rabbit is evidence that the 

 mammary development, like the uterine development, is dependent in. both 

 animals upon the influence of luteal tissue. It should, however, be made 

 clear that in the cases under observation the mammary growth was limited, 

 and that in pregnancy some further factor must come into play to complete 

 the development. The probable factor concerned in the case of the pregnant 

 rabbit is the subject of a communication by Hammond. 



In another paper Hammond and Hawk have remarked on the tendency for 

 the milk record of a cow to fall at about the time of oestrus, and it seems 

 possible that such periodic variation in milk secretion may depend partly upon 

 an anabolic influence on the part of the corpus luteum if the development of 

 this organ in the Dog, the Rabbit, and Dasyums is correlated with a building- 

 up of mammary isssue, rather than with the actual secretion of milk. 

 Furthermore, it is known that in the Sheep, which, like the Cow, is 

 polycestrous, the corpus luteum spurium attains its maximum development 

 very rapidly, being soon succeeded by degenerative changes, so that such 

 influence as this organ may possess upon the uterus and mammary glands 

 must be of very brief duration. 



Lastly, reference may again be made to the observations recorded by 

 Heape, Noel Paton, Blair Bell, and others of non-pregnant bitches (in some 

 cases virgins) secreting milk several weeks after oestrus, and frequently at 

 about the time when they would have given birth had they been pregnant. 

 Mr. F. Reynolds, of Devizes, has informed us that he also has observed 

 instances of the same phenomenon, and we have reason to believe that such 

 cases among bitches are far commoner than is ordinarily known. They are 

 to be explained as following upon an increase in certain individuals in the 

 activity of the corpora lutea. 



Steinach and Athias have recorded mammary growth as a result of 

 transplanting ovaries into previously castrated male guinea-pigs, but to 

 what precise ovarian elements the influence is to be attributed has not been 

 made clear. Steinach states that the mammary glands reached a degree 

 of development comparable to that of pregnant females, and sufficient to 

 admit of the manufacture of milk and suckling of young, fat globules being 

 found in the secreted fluid. 



