An Experimental Investigation of the Mechanism of Milk Secretion, With Special Reference to the Action of Animal Extracts

The mammary gland is, as regards its secretory activity, not under the direct influence of the nervous system. 2. Agents which cause its activity and also those which produce inhibition of its action reach it by means of the blood‐stream. 3. The organs of the body which produce hormones possessing the power of stimulating the mammary gland to activity are (a) pituitary body, (b) corpus luteum, (c) pineal body, (d) involuting uterus, (e) the lactating mammary gland itself. 4. The pituitary body is in this respect the most powerful. Its active galactagogue substance is formed in the posterior lobe of the gland, and is not specific to mammals, being present also in the pituitary gland of the bird. 5. Hormones inhibitory of mammary secretion are produced by the fœtus and placenta. 6. Drugs such as pilocarpine, which cause marked activity of most other glandular organs, and others, such as atropine, which inhibit the secretion of most glands, have no effect upon the secretion of the mammary gland. 7. Since the action of these drugs in promoting or arresting secretion of ordinary glands is in all probability exerted through nerves which are distributed to the secreting cells, it is concluded that there are no such nerves in the mammary gland. This conclusion is supported by the fact that neither section of the nerve trunks supplied to this gland nor their faradic stimulation appears to have any influence on the secretion of milk.