Effects of Extracts of Posterior Lobe of Pituitary 95 



been confirmed for the cow by Houssay). He obtained, however, an in- 

 hibitory action from extract of placenta, which, when injected into a vein 

 just previously to the injection of pituitary extract, prevents the effect of 

 the latter from influencing the mammary gland. It is reasonable to con- 

 clude from this that placenta extract contains a chalonic autacoid which 

 restrains the outpouring of the secretion of the mamma and antagonises 

 the hormonic action of the pituitary autacoid. 



Galactagogue autacoids are also contained in extracts of other organs 

 than the pituitary, viz., the corpus luteum of the ovary, the involuting 

 mucous membrane of the uterus after parturition, the lactating mammary 

 gland itself, and to a slight extent the pineal gland. Their effect on 

 the mamma is exactly like that of the pituitary galactagogue, but the effects 



a 



d. 



FIG. 66. Electric change accompanying the flow of milk from the mammary gland under 

 the influence of a dose of pituitary extract administered intravenously. 



a, record of string galvanometer : each millimetre of ordinate = 20 microvolts ; b, record of drops 

 of milk ; c, time in seconds ; d, signal of injection. The waves on a are respiratory. 



on blood-pressure are either nil or are different from that of pituitary 

 extract. Their galactagogue action will be described later. 



The blood, even in non-lactating animals, sometimes contains enough 



o o 



galactagogue autacoid to provoke the mammary secretion of a lactating 

 animal, although the other effects of pituitary extract are not seen. In 

 one experiment performed by me, as little as 5 c.c. of the blood-serum of a 

 guinea-pig injected into a lactating cat provoked a marked secretion from 

 a mamma the nipple of which had been incised, without producing any 

 effect on the blood-pressure. 



The action of pituitary and other extracts in causing secretion from the 

 gland is accompanied by a change in the electric potential of the organ 

 (fig. 66), so that the alveoli tend to become negative to the duct. This 

 change is somewhat similar to that which is produced in other secreting 

 glands which have been investigated. 



From what has been stated regarding the mammary gland, it is obvious that 

 this is an organ which is singularly under the influence of autacoids circulating in 



