424: PHYSIOLOGY. 



The secretion of milk is an example of a secretion that is eminently 

 the result of the metabolic activity of the secreting cell. The blood 

 is the original fountain of the milk,, but it becomes milk only by the 

 action of the cells of the mammary gland: a metabolism of those 

 cells. 



Ottolenghi has found in the active mammary gland of guinea- 

 pigs the presence of "Ninsen's globules," which are due to two 

 causes: first, an increase of the nuclei of the epithelium of the 

 gland ; and second, an infiltration of the gland cells with leucocytes. 

 This theory is opposed to that of Heidenhain, and makes the milk 

 secretion chiefly a disintegration of the nuclei of the epithelium of 

 the gland rather than a breaking up of the protoplasm. 



Ottolenghi also saw in the milk glands, with islands of active 

 gland tissue, other islands of a colostrum type a type of relative 

 rest. 



Fig. 158. Mammary Gland of the Dog, Second Stage of Secretion. 

 (HEIDENHAIN.) 



Colostrum. At the beginning of the period of lactation milk is 

 of a peculiar character and has received the name of colostrum. 

 This term is also applied to the milk appearing during the first week 

 after confinement. Colostrum is acid, possesses a yellow color, which 

 becomes white toward the fourth day. It is viscid and has a mean 

 density of 1.056. It contains, in addition to the fat-globules, colos- 

 trum-corpuscles. These are the degenerating polyhedral cells which 

 filled the vesicles previous to lactation. 



I have found that infusion of dried mammary gland decreases 

 the pulse and increases arterial tension. The blood-pressure rises 

 after removal of the main vasomotor center. 



Functional Variations in Milk. A substantial amount of nour- 

 ishment augments the quantity of milk. Drinks have the same 

 effect. An exclusive meat diet augments the proportion of fat in 

 the milk; a small meat allowance in a mixed diet increases casein 

 and diminishes the sugar. A vegetable diet diminishes the total 



