of incredulity were we to set it forth without a prologue far more lengthy than our space permits. Yet Dr. Gaskell may be right. We can but guess as to the nature of the prime functions of the thyroid and parathyroids. For many geological epochs they have not been exercised. But whatever else they did when they were indispensable constituents of the organism, their activity was accompanied by the secretion of colloid. Colloid is not made by other organs; therefore the otherwise obsolete thyroids are retained. It is of course not impossible that, in a certain degree, Nature, like a thrifty housewife, finds a new use for superseded apparatus; but we are probably justified in believing that the use is never really new. Not wanting the organ for its original specific purpose, Nature relegates to it alone work which hitherto it had shared with other of her tools. A comparatively short while ago the attention of physiologists was wholly concentrated upon the obvious or prime functions of organs. Muscles contracted. The stomach digested. The pancreas secreted pancreatic juice. The brain made thought. Now they understand, to put it somewhat metaphorically, that gastric juice is made in the calves of the legs; the ferment of pancreatic juice in the small intestine; thought of a certain emotional quality in the large intestine. The chemistry of the laboratory is far behind the body’s chemistry. We cannot detect in the blood coming from contracting muscles the stimulant—possibly a precursor of pepsin—to which the stomach reacts, although the magical benefit of exercise seems to prove that there is a chemical connection between the activity of the muscles and the activity of the glands of the alimentary canal. It has been proved by experiment that a substance produced in the epithelium of the small intestine is the messenger upon whose call depends the potency of pancreatic juice. The clearing of the brain effected by a judicious pill shows that poisons of some kind are absorbed into the blood from an overloaded large intestine. None of the organs lives altogether for itself. The chemical products which it throws off, absorbed by the blood, regulate the activity of other organs. Formerly the several parts of the body were looked upon as independent. Their activity was regarded as a direct response to the commands of the nervous system. If it varied in kind, the variations were supposed to depend upon the quality of the nervous impulses which reached the organ. Evidence is rapidly accumulating that many exhibitions of function are evoked by the calls of “hormones,” or chemical messengers, not by command of the nerves.