Durig and Zuntz1 made a voyage to Teneriffe, one of the Canary Islands (situated at about the latitude of Florida), and there ascended a volcano which rises to a height of 3160 meters. They found no essential difference in their metabolism from that at Col d'Olen (2865 meters) except a slight increase due to a quickened rate of respiration which they ascribed to the effect of sunlight.

1 Durig and Zuntz: "Biochemische Zeitschrift," 1912, xxxix, 435.

The results of these varied experiments confirm the independence of the metabolism of variations in atmospheric pressure as regards all the customary habitats of mankind. The beneficial properties of mountain air may be largely the same as those derived at watering-places, i. e., outdoor life, cool air, exercise, diversion through change of scene, mental rest, and, finally, suggestion of benefits received. The dry, crisp air undoubtedly benefits catarrhal disturbances, which are, on the other hand, aggravated by the climate of the sea-shore.

In the search for conditions which might reduce the intensity of metabolism, the influence of the internal secretions of the sexual glands has been prominently considered. Careful experiments of Liithje,1 however, show that castration in dogs of both sexes has no influence on the metabolism. It is said, however, that removal of the ovaries reduces for a time the number of red blood-corpuscles, and it is suggested that ovarian insufficiency may be the cause of chlorosis.2

Grafe3 has analyzed 29 cases of stupor, and in the majority of individuals has found no variation from the usual normal metabolism. In 8 cases, however, there was a metabolism which was between 17 and 39 per cent, lower than normal.

It has already been stated that Means, using the new Du Bois formula for surface area, could find no departure from the normal metabolism in simple obesity.

Means4 finds a diminished metabolism in hypopituitarism with accompanying obesity. This condition of dystrophia adiposogenitalis is stated by Cushing5 to show an abnormally high tolerance for carbohydrate, whereas in acromegaly the tolerance is decreased. In acromegaly the basal metabolism is increased.1

1 Luthje: "Archiv fur exp. Path, und Pharm.," 1902, xlviii, 184.

2 Breuer and v. Seiller: Ibid., 1903,1, 169.

3 Grafe: "Deutsches Archiv fur klin. Med.," 1911, cii, 15.

4 Means: "Journal of Medical Research," 1915, xxxii, 121.

5 Cushing: "The Pituitary Body and Its Disorders," 1912.

Forschbach and Severin2 (Minkowski's clinic) do not agree with Cushing, and conclude that in the most varied affections of the hypophysis (acromegaly, dystrophia adiposo-genitalis, hypophyseal tumors) there is always hypoglycemia and increased carbohydrate tolerance.3 This is illustrative of the disagreement among the best authorities upon the influence of the internal secretions.

Cushing and Goetsch4 and, before them, Gemelli,5 have noticed that in hibernating animals the pituitary gland not only diminishes in size, but that the cells of the pars anterior completely lose their characteristic staining reactions.

The literature regarding the action of the internal secretions upon metabolism is very large. Much of it is crudely unscientific. Where several unknown factors are interacting, as happens in this field of study, it is pleasant to give the fancy full play, and this is also a perfectly harmless occupation provided such mental activity does not develop into hallucination. Du Bois, in writing concerning exophthalmic goiter, makes the ironical proposal, "For the purpose of simplicity in this paper one may consider the symptoms of exophthalmic goiter to be caused by hypersecretion of the thyroid, and allow the reader to select for himself those cases in which he believes other glands to be involved".

The thyroid gland is a gland whose internal secretion profoundly affects the amount of general metabolism. No other gland compares with it in this regard. This influence is apparently brought about by a substance called thyroiodin, which, when produced in normal quantities, maintains the proper functions of the nervous system. A subnormal production reduces the activity of the nervous system and incidentally the quantity of metabolism. An overproduction increases the irritability of the nervous apparatus and raises the metabolism. Myxedema is a condition in which the thyroid gland has atrophied and its secretion is no longer available. Exophthalmic goiter presents the opposite phase, since here a superabundance of thyroidin is believed to be produced. Symptoms somewhat akin to the latter condition may be induced in normal animals and man by ingesting thyroid extracts.

1 Magnus-Levy: "Zeitschrift fur klinische Medizin.," 1906, lx, 179.

2 Forschbach and Severin: "Archiv fur exp. Path, und Pharm.," 1914, lxxv, 168.

3 For a good review of the literature read Simpson, S.: "American Medicine," 1914, ix, 219.

4 Cushing and Goetsch: "Journal of Experimental Medicine," 1915, xxii, 25.

5 Gemelli: "Archives pour la science medicale," 1905, xxx, 341.

Magnus-Levy1 found the carbon dioxid output increased after giving a normal man thyroid extracts. Fritz Voit2 finds the same to be true of a dog, and also that more protein is metabolized. It is this latter action which contraindicates thyroid feeding in obesity. However, Rheinboldt3 states that a man fed with thyroid extracts may be maintained in nitrogen equilibrium if much protein be allowed in the diet.

That the thyroid has a profound effect upon the endogenous protein metabolism is evidenced by the fact that after its removal in the dog the usual increases in protein metabolism which follow the administration of phlorhizin4 (see p. 460) or which follow partial asphyxia6 do not occur.