LACTATION 



575 



formation of alveoli proceed rapidly, so that by the twenty- 

 fifth day of pregnancy the whole surface of the abdomen has 

 become covered by mammary gland tissue, which may be half 

 a centimetre thick. This tissue is seen in sections to consist 

 for the most part of alveoli, in the cells of which fat globules 

 are in process of formation. 



From about the ninth day onwards to the twenty-fifth it 



FIG. 140. Section of mammary gland (human) showing developing alveoli. 

 (From Schafer, after von Ebner.) 



b, connective tissue ; ri, undeveloped alveoli ; d', partially developed 

 alveoli ; <j, blood-vessel ; in, portion of duct. 



is usually possible to squeeze a watery fluid from the nipples. 

 During the last days of pregnancy this fluid assumes the char- 

 acteristics of normal milk, so that by the time of parturition, 

 which occurs in the rabbit on the thirtieth day after conception, 

 the glands are full of milk. 



The multiparous rabbit differs from the virgin in pos- 

 sessing ready-formed alveoli at the beginning of pregnancy. 



