THE UDDER OF THE COW 3 



time the milk decreases, the cow loses tone and finally with 

 difficulty gives a negligible quantity of milk which is gray- 

 ish-yellow, thin and watery. 



In general the first milk secretion is produced through 

 reflex stimulations at parturition. The normal milk secre- 

 tion is only produced through birth. 



Milk secretion can be produced however under other 

 circumstances, as during oestrum. This is of little im- 

 portance, as a rule, and the udder soon loses its tone 

 again (spontaneous milk secretion). 



Experimentally it is possible to 

 produce an atypical milk secretion 

 through stimulation of the correspond- 

 ing nerves. 



The above mentioned method of 

 producing milk secretion is maintained ^.^ 2.-ve«seis of the ud- 

 through mechanical stimulation by v.e.t=fnielT7^^.stnc 

 the sucking of the calf or by the hand f «""= vena uberi. 

 of the milker. Without these mechani- "" =sup7amlmm8ry 

 cal factors the milk quickly diminishes. 



The milk secretion is therefore introduced by par- 

 turition and maintained through mechanical stimulation 

 (milking). 



This mechanical stimulation however cannot sustain 

 the milk secretion indefinitely, as the milk secretion di- 

 minishes usually about two months before the next birth. 



The lactation period can only be extended by mechani- 

 cal stimulation when no impregnation has taken place. 

 This can be induced for from fifteen to eighteen months, 

 especially after castration; in every case however a gradual 

 diminution occurs. 



In this condition the blood supply is decreased and the 

 udder is poor in liquid and dry (diminished lymph). 



The reflexly produced activity of the udder cells dis- 

 appears simultaneously with the blood supply and in con- 



