but what we have incorporated into modern therapeutics in the way of animal products lends at least some theoretical justification to the ancient use of the dried organs of various animals.  It is but a few years since the “ductless glands”—­such organs, as, for example, the thyreoid gland (an organ situated in the front of the neck, a small affair in its normal state, but prominent and even pendulous when by its permanent enlargement it comes to constitute a goitre)—­were looked upon as puzzles, as structures destitute of any known function.  Some observers even affirmed that they had no function, though the constancy of goitre in cretins ought to have shown the fallacy of this allegation in the case of the thyreoid.  We do not now need to be told that the thyreoid gland plays a very important part in the economy, for we know that its surgical removal gives rise to a special disease known as myxoedema, which, in addition to its physical manifestations, is characterized by impairment of the mental powers.  Consequently, this ductless gland—­a gland, that is to say, which has no obvious canal by which it throws off any product of its activity—­must elaborate some material that is necessary to the health of the organism and is imparted to the blood.  That material, whatever it may be, is termed an “internal secretion.”  Some of the internal secretions have turned out to be of singular value medicinally.  It is apparently not the ductless glands alone that furnish internal secretions; the glands that are provided with ducts and yield a definite and observable product secrete also a substance (perhaps more than one) which they give up to the blood.

Prominent among the therapeutic advances of the century is the direct reduction of the high temperature of sunstroke and certain fevers by the use of cold.  Although foreshadowed by Currie early in the century by his use of cold affusion in the treatment of scarlet fever, it did not come into general use until the closing decades.  It is employed principally in typhoid fever, on the theory that a condition of high fever is in itself a source of danger quite distinct from the other injurious effects of a febrile disease.  On the other hand, the employment of high degrees of heat has of late been shown to be a potent agency in the treatment of certain forms of disease, notably in various affections classed as rheumatic.  Applications of very hot air, provided it is thoroughly dry, are borne without serious discomfort, and their employment promises to be of greater service in the conditions in which it is resorted to than that of any other agent.

A revelation in the treatment of heart disease has been effected by the Bad Nauheim system of effervescent baths and resisted exercises.  It is not only functional disorders of the heart that are relieved, but grave organic diseases also.  Somewhat elaborate explanations of the way in which the treatment proves beneficial have been given, but they are not altogether satisfactory.