292 THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



the cord, and particularly the results of section immediately 

 below the medulla, are recalled. That a single stream of im- 

 pulses from the cerebral centers can sustain the entire function 

 that is to say, that part of it under nervous control scarcely 

 needs, under these conditions, to be emphasized. 



An important characteristic of the functions of the mam- 

 mary glands, however, is that their dependence upon their 

 nervous supply is not as great as is the case with other organs. 

 This is readily accounted for when the identity of the liquid 

 portion of milk is realized. The blood-plasma must undergo 

 but little change during its conversion into milk-plasma; in- 

 deed, it is probably merely filtered through the membrana 

 propria and the epithelial layer of cells in the lobules and thus 

 becomes charged with their products. Leucocytes are the main 

 source of the latter; Kadkin 18 found them both in the epithe- 

 lial lining and alveolar cavities, "wherein disintegration of 

 their nuclei supplies the milk with a proportion of its nuclein, 

 the remaining amount of the latter being furnished by the 

 epithelial cells." These bodies and the oxidizing substance of 

 the blood-plasma not only transfer to the milk their immuniz- 

 ing qualities, but the oxidizing substance is itself a source of 

 functional energy through which leucocytes and epithelial cells 

 are caused to endow the milk with its nutritive principles. 

 Much of the organ's work is therefore automatic. 



While "the secretion continues and is not arrested even 

 when the sympathetic as well as the spinal nerves are cut," 

 control experiments soon show that, as was the case with 

 Laffont's animal., the flow, though not arrested, is reduced even 

 when only one set of nerves is cut. This indicates, when con- 

 sidered along with the fact that stimulation of the mammary 

 end of the nerve increases the gland's activity, that the nervous 

 supply must not be disregarded, and it also suggests that the 

 sharp line drawn between "active" and "passive" activity, in 

 the case of other organs, and which mainly depends upon 

 nerve-impulses to secreting structures and vascular walls, is 

 scarcely applicable here. Indeed, we are doubtless dealing 

 with mere fluctuations of activity, called forth, during lacta- 



18 Kadkin: Inaugural Dissertation, 1890. 



