The oxygen of the air, upon reaching the tissues through the blood by means of the respiration, acts upon the organic substances which are to enter in the formation of new cells. 2

The products of this transformation are the organic materials which form the physical basis of muscle, nerve, connective tissue and mucous substance. None of these substances are present as such in the blood, but are formed within the tissues from the albumen. With them, the inorganic salts form combinations by virtue of chemical affinities, and thus new cells are formed. With the formation of new cells there occurs at the same time a destruction of the old ones, resulting from the action of oxygen on the organic substances forming the basis of these cells. This oxidation has, as a consequence, a breaking down of the cells themselves.

The ultimate results of this combustion of the organic substances are the formation of urea, uric, sulphuric, phosphoric, lactic and carbonic acids, and also water. Some intermediate members of the series, as, for instance, hypoxauthiu, acetic and butyric acids, etc., need not be mentioned with this therapeutic method, because, so far as our present knowledge of them extends, they play a very subordinate role. Urea, uric acid and sulphuric acid are the result of the oxidation of the albuminous substances, while phosphoric acid is produced by the oxidation of lecithin contained in the nervous tissue, brain, spinal cord and blood corpuscles. Lactic acid results from the fermentation of milk-sugar, and finally breaks down into carbonic acid and water.

The final products of the oxidation of the organic substances are urea, carbonic acid and water. These, together with the salts set free, leave the tissues, and thereby give place to less fully oxidized organic bodies, which in turn finally undergo the same metamorphosis.

The products of this retrograde tissue change are conveyed through the lymphatics, the connective tissue and the veins, to the gall-bladder, lungs, kidneys, bladder and skin, and are thereby removed from the organism with the excretions, such as the urine, perspiration, faeces, etc.

The importance and dignity of the function of the connective tissues were established after the researches of Virchow and Von Recklinghausen led to a closer study and demonstrated its fertile activity. That which formerly seemed only intended as a filling in or protective covering appears now as the matrix, in which the minute capillaries carry the plasma from the blood to the tissues and return the same to the blood vessels; at the same time it serves as one of the most important breeding places of young cells, which are capable of developing out of the embryonic latent forms to the most differentiated structure of the body.