558 THE PHYSIOLOGY OF REPRODUCTION 



ever, is believed to be due partly to the larger globules of fat 

 meeting with greater resistance in passing through the ducts 

 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 



Fig. 137. — Section of mammary gland (human) in full activity. 

 (From Schafer, after von Ebner.) 



a, a', a", alveoli variously cut and distended by secretion ; g, g\ com- 

 mencing ducts ; i, connective tissue. 



was immediately afterwards millced. By the time the udders 

 had been 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. 



Three different hypotheses have been put forward regarding 



' Lehmann, "Beitrage zur Pbysiologie der Milchbildung," Die land- 

 wirthschoftlichen Versuchs-Stationen, vol. xxxiii., 1887. 



