562 SWALE VINCENT 



clear from other curves given in the same paper, that a marked action on 

 the secretion of milk may be obtained with doses too small to produce 

 any appreciable effect on the blood pressure. The galactagogue principle 

 is insoluble in alcohol, but is not destroyed by standing in it ; its activity is 

 not impaired by repeated boiling nor by standing for some weeks in solu- 

 tion in a sterilized condition. The active substance is present, not only 

 in the corpora lutea of lactating animals, but also in those obtained when 

 lactation is not proceeding. In one case MacKenzie obtained a flow from 

 the gland of a non-lactating cat. 



Galactagogue principles can be extracted only from pituitary, corpus 

 luteum, pineal, mammary gland, and the involuting uterus. Other gland 

 extracts appear to be inactive in this respect. MacKepzie reaches the 

 conclusion that the organs above mentioned produce "hormones" pos- 

 sessing the power of stimulating the mammary gland to activity. The 

 evidence in favor of this theory is so far quite inadequate. As the 

 present writer has had frequent occasion to point out, the mere fact that 

 an extract of an animal tissue produces certain pharmacological effects 

 is sufficient perhaps to suggest a possible internal secretion on the part of 

 the tissue, but is by no means proof that such secretion actually oc- 

 curs. 



There are now numerous cases on record in which medical men have 

 treated cases of deficient milk secretion in women by the administration 

 of corpus luteum extracts. The results are said to be good. 



Many attempts have been made to replace the internal secretion of 

 the corpus luteum by means of injection of extracts. These attempts have 

 not given very conclusive information, because the extracts have not al- 

 ways been prepared in the same way, and because sufficient control ex- 

 periments with extracts of other organs have not yet been carried out. 

 Frank found that corpus luteum extract, injected intravenously in suffi- 

 cient concentration, proves rapidly fatal in consequence of intravascular 

 thrombosis. Corpus luteum substance obtained from a foreign species was 

 without effect on the cyclic changes of the uterus and did not permit the 

 production of deciduomata (vide, p. 566). Loeb (p) (1917) states that 

 injection of cow corpus luteum extracts in NaCl solution does not prevent 

 necrosis of the deciduomata, nor does it prolong the life of deciduomata 

 in guinea pigs. 



Several years ago the present writer, in conjunction with Dr. E. H. 

 A. Marshall, performed a series of experiments designed to test the 

 theory that the estrous cycle is determined by an internal" secretion on 

 the part of the ovary. Extracts were made from ovaries in a pro- 

 estrous or estrous condition and injected subcutaneously into a bitch at 

 a period as remote as possible from the estrous one. In some of these 

 experiments a swelling of the vulva and other slight signs of the estrous 

 condition were induced, but the results were not decisive enough to war- 



