734 SCIENCE PROGRESS 



epithelial cells no longer multiply and mitoses are absent from 

 them, but each individual cell increases markedly in size and 

 commences to secrete. The cells of alveoli and tubules become 

 arranged in a single layer, and as a result of their secretory 

 activity the alveoli and ducts become greatly distended. It is this 

 second stage that is the more noticeable in external examination. 



An interesting correlation is seen between the formation and 

 growth of the corpus luteum and the growth phase of the 

 mammary glands. As soon as the corpus luteum is formed the 

 mammary gland starts to grow. This growth is noticeably 

 increased after the body is fully formed, a stage characterised by 

 the presence of plentiful granules in the lutein cells. Later the 

 corpus luteum reaches its maximum and remains constant, and 

 shortly after the cells of the mammary gland cease to multiply. 

 This correlation, which holds good whether the female be 

 pregnant or not, suggested, taking into account the other evidence, 

 that it was very probable that the corpus luteum, in addition to 

 its other functions, is intimately connected with if not indeed 

 the point of origin of the stimulus inciting growth in the 

 mammary glands. 



Other evidence regarding the relation of the two structures 

 was already in existence when the foregoing conclusion was 

 independently arrived at. Ancel and Bouin (2) showed that if 

 corpora lutea are produced in the rabbit, either by copulation 

 with a male previously rendered sterile or by artificial rupture 

 of the follicle, a growth of the mammary gland follows. This 

 growth, very noticeable about the fourth day, ceases about 

 the fourteenth day and regression then takes place. 



Similar experiments have been performed (16) which confirm 

 these results in their essential points. It was found, however, 

 that the rupture of the ripe follicles was not invariably followed 

 by the formation of corpora lutea, but this provided a strong 

 piece of negative evidence. The results may be summarised as 

 follows. 1. If the rupture of the follicle was followed by the 

 formation of corpora lutea there was also a growth of the 

 mammary glands. The amount of growth in fourteen or fifteen 

 days was about equal to that in the normal pregnant animal of 

 twelve days. 2. On the other hand, if the follicular rupture was 

 not succeeded by the formation of corpora lutea, there was no 

 growth of the mammary glands, although the operation per- 

 formed was precisely similar in the two cases. 



