Milk Secretion. 



of its growth through nervous influences. On the other hand it 

 has been observed that in other conditions, in which there exist 

 also a diversion of great quantities of blood from the genital parts 

 for the supply of other organs, as for instance after operation on 

 very large tumors in the region of the genital organs, no secre- 

 tion appears even when the udder is prepared for the secretion. 



As a matter of fact the secretion may commence before birth, 

 and even in early abortions, or if the fetus dies. At times when 

 the uterus is only so slightly distended that the quantity of blood 

 set free after abortion is hardly sufficient for an effective hypere- 

 mia of the milk gland, the secretion of milk may result (Sinety, 

 Kreidl, Mandl). Therefore the explanation that the quantitative 

 influences of the blood may give rise to a stimulation of the milk 

 secretion (Freund), can scarcely be accepted. Consequently the 

 qualitative changes of the blood must be considered as more prob- 

 able factors. 



Authors have diversified opinions upon this question. 



While some accept the view that substances are eliminated 

 from the impregnated organs, or by the fetus itself into the blood 

 of the mother by internal secretions, and that these act as stimu- 

 lants on the milk glands, others believe that the factors causing 

 lactation lie in the assimilation of certain nutritive substances. 



The supporters of the theories of "stimulation substances" 

 (Sinety, Halban, Starling) take the stand that stimulating sub- 

 stances which cannot be utilized for the cellular growth and cellu- 

 lar activity, contrary to the nutritive substances, cause the devel- 

 opment of the gland during pregnancy, and at the same time pre- 

 vent it from secreting (stimulines, hormones [I stimulate], sub- 

 stances of pregnancy). Development of the gland and prevention 

 of secretion may, of course, be the action of one and the same sub- 

 stance (Hildebrand, Starling), or its development, as long as the 

 growth continues, may retard secretion. With birth the stimula- 

 tion of growth and development ceases, and secretion commences. 



Contrary to this, the theories of nutritive substances empha- 

 size the fact that the glands at times may start the specific activity 

 without the presence of certain stimulines, probably through nutri- 

 tive substances which are present in the blood at various times. 



Eauber attempts to explain the activity of the gland after 

 birth by declaring that after the expulsion of the fetus a nutritive 

 material becomes available, which has served prior to birth for 

 the preparation of nutriment for the offspring. While the ex- 

 planation of the author that the lymph cells play the most impor- 

 tant part in this can no longer be considered, still it furnishes 

 the basis for all new theories relating to the action of nutritive 

 substances. 



These views were strengthened in 1908 by Schein by the state- 

 ment that during pregnancy the mother animal, in order to meet 

 the requirements of the fetus and of the impregnated organs, en- 



