1911.] The Action of Animal Extracts on Milk Secretion. 19 



passed off after three or four minutes, during which time 30 to 40 

 large drops of milk were recorded. This, it must be remembered, was from 

 two of the mammary glands only (usually two were led off to the one drop- 

 recorder), representing about one-fifth of the whole glandular mass. But it 

 lasts only a short time, in which respect it differs from the effect which the 

 same extract produces upon the urinary secretion, the rate of which may be 

 increased during many minutes after the injection, and even to some degree 

 for a prolonged period. In the case of the urinary secretion, a second or 

 " repeat " dose of posterior-lobe extract, given within a period of half an hour 

 or less, causes a renewed increase of urine secretion, although this may be now 

 unaccompanied by a repetition of the rise of blood- pressure which accompanies 

 the first dose.* But the effect of a repeat dose upon the secretion of the 

 mammary gland is much less than that produced by the first dose, and in 

 some cases fails to be recorded by the " nipple method," although it can be 

 sometimes observed by the " exudation method " ; and such repetition 

 produces a smaller result than the previous one. 



We find that the galactagogue substance of the pituitary body is not 

 present in the pars anterior, but only in the pars intermedia and pars posterior 

 of the gland. It is not yielded to absolute alcohol, although a very small 

 amount of water in the alcohol used will suffice to extract it. It is not 

 •destroyed by contact with absolute alcohol (at least within a reasonable 

 period), nor by repeated boiling, nor by prolonged keeping in the dry state 

 (we have obtained marked effect from dry posterior-lobe substance which 

 has been kept some years in a stoppered bottle). The galactagogue action 

 runs parallel in time with the action of the extract upon the systemic blood- 

 vessels, which are contracted by posterior-lobe extracts.f It is probable, 

 however, that, as in the case of the kidney, the blood-vessels of the mammary 

 gland do not share in the general constriction which this extract produces. 

 But we have not yet succeeded in definitely determining by a plethysmo- 

 graphy method whether the vessels of the gland dilate during the increased 

 secretion, although to judge from the appearance of the cut gland this would 

 seem to be the case. This is a point which must be the subject of further 

 investigation. 



Another extract which in our hands has yielded a definite positive 

 result is extract of fresh corpus luteum, prepared with Einger's solution. The 

 ■effect is quite distinct but less decided than with extract of posterior lobe of 

 pituitary : for, instead of some 30 to 40 drops, not more than 5 drops of milk 

 were yielded by the nipple method after injection of 5 c.c. of a corpus 

 * Schafer and Herring, op. tit. 



t Oliver and Schafer, ' Journ. Physiol.,' vol. 18, 1895. 



C 2 



