THE REPRODUCTIVE 



221 



When lactation is suspended the breast at first secretes a fluid in 

 every way resembling colostrum, and eventually returns to the dor- 

 mant state, in which the cells are again small and granular and the 

 stroma is relatively abundant. 



As the glandular portion of the breast enlarges during lactation, 

 the whole breast becomes increased in size, but this increase is not 

 proportional to the development of the alveoli, for the stroma is 

 reduced in amount, so that the lobules of the gland are closer to 

 each other. After the period of lactation is passed the alveoli 

 return almost to their original size, but the stroma is not repro- 



FIG. 196. 



Section from the mammary gland of a guinea-pig during lactation. (Michaelis.) The figure 

 represents sections of two acini and the margin of a third, separated by vascularized 

 areolar tissue, a, fat-globule, separated from the lumen by a mere film of cytoplasm ; 6, 

 projecting cell with two nuclei : c, two nuclei which appear to have been produced by 

 constriction of a single pre-existent nucleus. 



duced in fibrous form, but its place is taken by adipose tissue, the 

 amount of which depends upon the individual, being great in 

 those that are fat, and slight in those that are lean. In the 

 latter, therefore, the breast becomes soft and pendulous after 

 lactation has ceased. 



It is important to bear the above changes in the normal gland in 

 mind when examining the mamma for evidences of a tumor. When, 

 for example, the stroma is abundant and the glandular structures 

 undeveloped, as is the case before puberty, sections of the gland 

 may be mistaken for those of a mammary fibroma. 



