512 PHYSIOLOGY CHAP. 



temperature, caseinogen and lactose were formed. The latter is 

 preceded by the formation of a colloidal carbohydrate which is 

 identical not with glycogen, but, according to Landwehr, with 

 animal gum. These observations agree with what w r e have stated 

 in regard to the preponderating importance of alimentary protein 

 for milk production, and the amount of the respective organic 

 constituents of milk. We may reasonably conclude that the 

 mammary gland obtains from the serum-albumin of the lymph, 

 more particularly, the material for the synthetic formation of the 

 nucleo-protein and gluco-protein of which its protoplasmic granules 

 are composed. The different specific constituents of the milk 

 are derived from the decomposition of these and of the nuclear 

 substance. 



Arnold's subsequent work (1905) on the formation of the fat 

 of milk also gave results that entirely agree with the above view. 

 On studying the mammary gland of woman, cow, and rat under 

 the microscope, he saw that a copious secretion of fat could occur 

 without cellular degeneration ; that the fat always appeared first 

 inside the cell, in place of the granules of the cytoplasm (particu- 

 larly in the basal part opposite the lumen), while fat was never 

 seen round the cells. The mother substance of the fat must there- 

 fore be supplied to the cells in a dissolved form, which is after- 

 wards converted into fatty granules by the protoplasm. 



As regards the colostrum corpuscles, on the contrary, Popper 

 (1904) fell back on the conclusion that they are epithelial cells 

 detached from the alveoli or ducts, which on reaching the lumen 

 of the gland are still capable for a certain time of showing vital 

 phenomena, before they undergo fatty degeneration. Their origin 

 as gland cells is shown more particularly by the aspect of their 

 nuclei, which exactly resemble those of the gland cells, and are 

 clearly distinguished from those of the leucocytes by the reticular 

 arrangement of the chromatin. These and other data militate 

 against the foregoing view by which the colostrum corpuscles are 

 taken to be leucocytes. 



X. The evidence as to whether the secretion of milk is directly 

 or indirectly influenced by the nervous system, is of a conflicting 

 nature. Generally speaking, it may be said that a number of 

 everyday observations demonstrate the intervention of the 

 nervous system both in the development and in the secretory 

 activity of the mammary gland. 



The correlation between the genital apparatus and the 

 mammary glands is familiar to every one. The latter develop 

 gradually during gestation ; immediately after parturition the 

 milk secretion becomes very abundant, and persists throughout 

 the period of suckling. Moreover, during this period menstruation 

 usually ceases. These facts witness to a special trophic and 

 functional relation (a sympathy as was formerly said) between 



