Milk Secretion. 21 



tion commenced also in the virgin sister. In this instance nervous 

 connections may exist in the genitals of both individuals. Accord- 

 ing to the author's view this case is not an absolute proof of the 

 stimulation of the gland by hematogenic means. 



The lactation theories may be laid aside, and consideration 

 only be given to the fact that at birth, puberty, pregnancy, at the 

 conclusion of parturition and also in the disturbances of the gen- 

 itals influences are exerted on the milk gland the character and 

 action of which are still uncertain, although the results manifested 

 by the production of milk may readily be observed. Especially 

 typical and striking are the phenomena seen at puberty and during 

 and at the end of pregnancy. Exceptionally a condition may ap- 

 pear outside of these normal periods of the organs in females, and 

 in single cases even in male individuals, which permits the conclu- 

 sion that the glands react to special stimulation. Abnormalities 

 may occur in the anatomical structure of the gland, pathological 

 manifestations in the sense of inflammatory reactions, etc., may 

 also be observed, and exceptionally the usual functions may be 

 present or may develop, without their being accompanied by gross 

 anatomical changes of the gland ; these however are usually pres- 

 ent at the same time. 



These influences on the gland originate partially in the gravid 

 genital organs and the fetus; in other instances the germinal 

 glands and the disturbances of their functions are the cause of 

 these influences. 



Such influences may be classed according to the impulses 

 which lead to glandular activity, as follows (Halban) : 



1. Embryonic impulse action very transitory mastitis 

 neonatorum witches milk. 



2. Puberty lasting effect development of the gland. 



3. Oestrum action rapidly transitory hyperemia, inter- 

 stitial hemorrhages, disturbances to physiological lactation, secre- 

 tion. 



4. Impulse of pregnancy lasting between parturitions. 

 Lactation may be sustained for a long period of time by the 



regular drawing of the milk, and ceases in healthy udders only 

 when after frequent and absolute stasis of the milk (after about 

 eight days), the tissue becomes affected by inflammatory irrita- 

 tions (absorbtion and change of the condition of the epithelium), 

 or when the animals are soon to give birth to young. If no re-im- 

 pregnation takes place the lactation period may last longer, even 

 from one to two years although not to an unlimited extent. The 

 activity of the gland may be retained for a long time through the 

 sucking of the young, stimulation by milking, or artifical with- 

 drawal of milk. 



Frequent periodical and complete emptying of the milk cis- 

 terns acts favorably on the amount produced. In the cow two to 

 three milkings per day are sufficient to retain the udder in secretion. 



