450 MANUAL OF HISTOLOGY. 



Ranker's mews on the mamma and the lacteal secretion are 

 somewhat startling, but must occupy our attention here. From 

 a series of very carefully conducted examinations, principally 

 on the glands of guinea-pigs during and after pregnancy, he 

 feels justified in concluding that milk owes its orgin to the 

 entrance of countless leucocytes into the lumen of the gland- 

 vesicles. The emigrated lymphoid elements, he believes, pene- 

 trate the alveolar walls, passing through the single layer of 

 epithelial cells which line them. Arrived in the interior of an 

 ultimate acinus, the leucocytes undergo fatty metamorphosis, 

 and thus at length furnish the most essential and characteristic 

 ingredient of milk, viz., the milk-globules. Rauber, therefore, 

 discards the notion that the formed particles of the lacteal 

 secretion originate in the glandular epithelium, and represent 

 the elaborated products of its functional activity. He also 

 denies that previously formed milk globules, or colostrum cor- 

 puscles, ever pass through the alveolar walls. Thus the prim- 

 itive opinion advanced by Empedocles, describing milk as white 

 pus, is in a measure revived, and milk is held to be directly 

 derived from the white corpuscles of the blood. 



Preparations of mammary glands taken from animals still 

 suckling their young, according to him, invariably show the 

 intraglandular lymph-vessels replete with leucocytes, the stro- 

 ma similarly infiltrated, identical corpuscles in ^greater or less 

 abundance within the vesicles, and transitional forms between 

 lymphoid-corpuscles and milk-globules. These claims, granted 

 to be facts, and considered in conjunction with the circum- 

 stance that epithelial proliferation is not seen, would certainly 

 go far to make Rauber' s theory seem a somewhat plausible 

 one. Nevertheless, we require corroborative evidence from 

 others, before his views can be accepted as anything more than 

 an ingenious hypothesis. 



Rauber has also described the occurrence of a delicate stri- 

 ation within the epithelial cells of the alveoli. These striae are 

 said to be in all respects similar to those found in the secreting 

 elements of certain portions of the salivary glands and the 

 tubules of the kidneys. 



As regards the corpuscles of Donne, or colostrum bodies, 

 most authors regard them as the products of desquamation of 

 the alveolar epithelium, the latter being in a condition of fatty 

 degeneration (Winkler, De Sinety, Buchholtz, and others). 



