DAIRY FARMING DAIRYING. 283 



found between the individual epithelial cells. Eosinophil cells were 

 likewise observed in large numbers. 



An investigation of the contents of the mammary glands of pregnant 

 guinea pigs for a period of 4 weeks showed an alternating occurrence 

 of leucocytes and colostrum corpuscles; when both kinds were present 

 all of the different transformation stages were observed. This gives 

 rise to the question as to the origin of the colostrum corpuscles. 

 Michaelis concludes that they consist of leucocytes, and especially of 

 the mononuclear lympb corpuscles which have taken up fat globules. 

 In no case do they result from a fatty degeneration of the leucocytes, 

 as Rauber states, for in the first place they have a nucleus and in the 

 second place they show amoeboid movements. This accounts for the 

 mononuclear leucocytes, and the question arises as to the role of the 

 leucocytes with several nuclei. Michaelis found that they break down 

 after an active division of the nuclei has taken place. 



The fate of a lymph corpuscle which penetrates the epithelium of the 

 mammary glands is, therefore, ( L) that either it increases in size, takes up 

 fat globules, and becomes a colostrum corpuscle (always mononuclear), 

 or (2) after enlarging slightly the nucleus breaks up and then the cell. 

 As to the farther fate of the colostrum bodies, Michaelis was not able 

 to determine definitely; but the probability of their returning to the 

 lymphatics, as suggested by Czeruy, is excluded by their immensely 

 increased size. 



While the above refers to the condition of the mammary glands of 

 pregnant animals before parturition, the glands of suckling animals 

 present a totally different appearance. Here the interstitial connective 

 tissue has been reduced to a minimum, the acidophile cells have disap- 

 peared, and also the lymphatic corpuscles in the connective tissue. 

 There is hardly a leucocyte to be seen, but in their place clusters of free 

 nuclei are observed in the secretion, which in all respects resemble the 

 nuclei of the epithelial cells. Michaelis could plainly observe the expul- 

 sion of these nuclei, some of which still adhered to their cells. Other 

 investigators have made similar observations, but the fact that karyo- 

 kinesis had never been observed in the actively secreting gland made 

 this one of the darkest points in the etiology of milk secretion. All 

 are agreed, however, that the actively secreting glands contain a larger 

 number of nuclei than the reverting ones. As to the origin of these 

 nuclei, Michaelis was able to find polynuclear epithelial cells in which 

 direct cell division was taking place. Indications of this appeared 

 immediately after parturition, when nuclei of various sizes and shapes 

 were to be seeu. This had escaped previous observers. As a result of 

 his discovery the statement is made that the innumerable nuclei which 

 are present in the lumen of the milk ducts and alveoli are expelled by 

 the epithelial cells, in which they are formed by direct karyokinesis. 

 However, these nuclei do not occur in normal milk, as they are disinte- 

 grated through chromatolysis and form a homogenous mass of achro- 



