354 THE DUCTLESS GLANDS 



tracts of pituitary body, corpus luteum, pineal body, involut- 

 ing uterus, and lactating mammary gland all manifest a 

 galactagogue action, but the pituitary body produces the most 

 marked results. 



Gavin found that the daily yield of milk in cows is not 

 increased by the administration of corpus luteum and pituitary 

 extract. Schafer also reports that injection of pituitary extract 

 into a muscle of a lactating woman caused only a temporary 

 increase in the flow of milk. 



It has been suggested that the hypertrophy of the mammary 

 glands is brought about by some secretion produced during 

 pregnancy, which neutralizes the tendency of the cells to 

 discharge under the influence of secretion from the pituitary 

 and other organs. When this inhibitor is removed, the 

 hormones causing the discharge of the gland come into action, 

 and so cause the secretion. 



This seems likely from the experiments of Mackenzie, who 

 states that by injecting extracts of foetus or placenta together 

 with pituitary extract into a lactating animal, the action of 

 the pituitary is inhibited. 



In regard to the corpus luteum, there is a theoretical dis- 

 crepancy between the views of those who regard the body as 

 one of the building-up factors, and the results of Schafer and 

 others who find that corpus luteum extract produces an imme- 

 diate secretion. 



Hammond finds, as did previous observers, that the galac- 

 tagogue effect of pituitary extract is only temporary. The 

 effect is not muscular. The daily yield is only slightly increased, 

 and is not dependent on increased blood-pressure. The pitui- 

 tary gland seems not to be the origin of the ordinary changes 

 in Ihe mammary gland. Histological evidence points to a 

 direct action of the extract on the glandular epithelium. The 

 milk obtained after injection has a higher percentage of fat 

 than normal ; in the subsequent milkings, however, there is 

 a drop in the percentage of fat, although that of the other 

 ingredients remains normal. 



While the proteins, lactose, and ash are secreted in close 

 connection with the water of the milk, the amount of fat is 

 not so connected with the amount of water. The ratio of 

 "nitrogen to lactose" is relatively conMant throughout. 



Hill and Sutherland Simpson state that pituitary extract 





