Selective power of tissues, especially as illustrated in the mammary gland

Abstract

The question of the selective power of tissues, by which they can abstract from the medium in which they are placed those substances which are necessary for their life and function, opens up many problems of fundamental importance in biology. There are points of uniformity between all cells. Every cell respires. Every cell absorbs nutrient material and excretes the indigestible and the effete. But each cell is an independent unit which chooses for itself the substances required for its growth, its development and its functions; and some cells devote their energies to the elaboration of material not for their own individual needs, but for the fulfillment of a function beyond the narrow limits of their own cell-walls.

It is to.the study of this selective power that I shall devote my thesis. No tissue of the body seems to me to possess this prophetic power of selection in so eminent a degree as the Mammary Gland, engaged as it is in the elaboration of a material adapted to the requirements not of its own cells, not of the organism of which it forms a part, but of an entirely different organism. I propose to enter, after describing some of the most striking phenomena of selective activity as exemplified in other tissues into the subject of the Chemistry of the Mammary Gland and its secretion, with special reference to the production,in different species, of milk suited for the diverse needs of the sucklings of these species. The work on the Mammary gland and much of that on the chemistry of milk has been carried out by me in the Physiological Laboratory of Edinburgh University. As for the rest I hope to submit a digest and a criticism of the work of others, some of which may not be widely known, and all, I trust, will be of Physiological interest and practical importance.