590 



THE PHYSIOLOGY OF REPRODUCTION 



calculated that the udder of a cow could not contain the quantity 

 of milk which can be obtained from it at one milking, so that in 

 such cases at least it seems certain that the process of secretion must 

 be carried on during the time that the milk is lieing drawn. 

 Furthermore, the milk which is drawn latest has l>een shown to have 

 a different composition from that which is first obtained, the proportion 

 of solids to liquids undergoing an increase as the process of milking 

 is continued. This, however, is believed to he due partly to the 









Fig. 163. — Section of mammary glaDcl (human) during lactation 

 (highly magnified), a. Acini ; h, duct. 



larger globules of fat meeting with greater resistance in passing 

 through the duets and so being retained until the end of milking. 

 Lehmann ^ has recorded an experiment in which a solution of sulphin- 

 digotate of sodium was injected into a vein of a goat which was 

 immediately afterwards milked. By the time the udder had Ijeen 

 almost completely emptied, a blue tinge appeared in the milk. After 

 an interval of about an hour and a half the animal was again milked, 

 when it was found that the injected sulphindigotate had penetrated 

 in sufficient quantity to render the milk quite blue. 



1 Lehmann, "Beitrage zur Physiologie dei- Milchbildung,'' JJie landtvirth- 

 xrhfiftHi-hirii Versuchs-Stationen, vol. xxxiii., 1887. 



