was 1260-0 grammes. The ashes of the urine yielded a small amount of nickel. No tartaric acid could be found in the urine. The urine of the next days contained no trace of nickel. The fæces, which were of the usual consistence, contained no nickel on the first day, but considerable quantities on the second and third. They were dark brown, from the sulphuret of nickel, which is dark brown, when finely divided, and not blackish-green, like sulphuret of iron.

The experiments show that of large quantities of tartaric acid and its salts, ingested into the stomach, a small per centage may reappear in the urine. The great bulk is transformed into carbonates.

The following table exhibits the results of the above experiments:

Of the salt with potash and soda, a larger per centage appears in the urine.

Of tartaric acid, a much smaller per centage reappears in the urine than of oxalic acid.

Wöhler believed that free tartaric acid passed unchanged

into the urine, but did not do so when taken in combination with bases. This error has given rise to the theory, that the presence of alkalies in the blood was necessary for oxydation, and that by increasing the amount of alkali in the blood we could favour this process. Mialhe's treatment of diabetes, already found practically useless,' and experimentally made improbable by Lehmann' and Poggiale, thus loses its last foundation. Dr. Parkes was of opinion, that by the medicinal use of alkalies the quantity of sulphuric acid in the urine, which was to be considered as the product of oxydation of albuminous substances, became augmented. But the experiments of W. Clare do not support that opinion, so that the alleged use of the alkalies has become more than questionable.

The experiments of Morichini, quoted by Wöhler, on the passage of citric acid into the urine, are related with so many improbabilities, that we must leave them out of consideration. The only experiments worth noticing, previous to those of Buchheim, are by Gilbert Blane, who found that citrate of potash appeared in the urine as carbonate.

In eight different experiments by Buchheim, in which repeated and large quantities of free citric acid were taken, the urine was quite normal, and contained no trace of citrie acid. The citrates with three equivalents, one-and-a-half equivalents, and one equivalent of soda, respectively, taken in three different experiments, made the urine alkaline; but no trace of citric acid was found in the urine. The citrates with three equivalents and one equivalent of magnesia, respectively, caused diarrhoea, the fæces containing carbonate of magnesia. The urine was acid, and free of citric acid.

'Garrod, Gulston Lect. on Diabetes, Assoc. Med. Journ.,' 1857.

* Lehrbuch d. Physiol. Chemie,' 2d edit., Leipzig, 1853, vol. iii, p. 205. 3 Comptes rend.,' t. xlii, p. 198.

• Loc. cit.

Wöhler and Frerichs gave to a dog pure tannic acid, in doses gradually increasing from 0.5 to 60 grammes. The animal remained well, but the fæces gradually ceased to be discharged, though the appetite remained the same. The urine, in the beginning of the experiment, showed the normal yellow colour, which, however, gradually changed into a dark, lastly intensely brown colour, until at last it became brownish-black, and impervious to transmitted light.

The brown urine yielded a blackish-blue precipitate with salts of oxyde of iron, but no precipitate was produced in it by a solution of gelatine. Tannic acid, consequently, in its transit through the body, had become transmuted into gallic acid.

Salts of the suboxyde of iron produced a bluish-black precipitate in the urine, indicating the presence of pyrogallic acid. As this acid, in presence of ammonia, is easily transformed into humine-like bodies, it is reasonable to explain the black colour of the urine by the further decomposition of the pyrogallic acid, for which the ammoniacal condition of the urine afforded the opportunity. The dark colour and peculiar reactions of the urine continued for two days after tannic acid had ceased to be administered.

By the action of acids, alkalies, or ferments, tannic acid, taking up water, is transformed into gallic acid and sugar, according to the following formula:

C54H2O34 +8HO = 3(C14H8O10) + C12H12O12

22

Tannic acid.

Gallic acid.

Sugar.

It is probable that the metamorphosis of tannic acid in the human body takes place in a similar manner.

Kraut' took toluylic acid in doses of several grammes. He

This

felt no effect from it; the urine which was voided afterwards had a strongly acid reaction. It was evaporated to the consistence of a syrup, and extracted with alcohol. The extract was treated with oxalic acid, and again evaporated, and the residue extracted with ether containing some alcohol. left, on evaporation, a yellowish, crystalline mass, mixed with oxalic acid. It was boiled with carbonate of lime, when from the filtrate a lime-salt crystallized. This, after repeated crystallization, and decomposition with dilute warm hydrochloric acid, yielded, on the fluid cooling, a crystallized acid (toluric acid) which, after recrystallization from boiling water, was obtained pure in crystalline colourless plates. The solution in alcohol on spontaneous evaporation deposited large rhombic crystals. This acid has the composition CHINO. It forms salts with baryta, and oxyde of silver, and the alkalies, which are more soluble in hot than cold water. In cold fuming hydrochloric acid, toluric acid is soluble. If the solution, after short ebullition, is allowed to cool, toluric acid crystallizes from it unchanged. But when this solution is boiled during several hours, the hydrochloric acid being replaced as it evaporates, and is lastly evaporated to dryness, a residue remains, which may be separated in two by treatment with water. This fluid leaves an amorphous substance undissolved, which may be recognised as toluylic acid, and transformed into the silversalt; the solution, after saturation with ammonia, evaporation, and addition of alcohol, leaves a precipitate, which is glycocoll. It may be identified by its property of dissolving oxyde of copper in watery solution, in which alcohol produces a precipitate of oxyde of copper glycocoll.

Toluylic acid, therefore, like benzoic acid, combines with glycocoll in the animal economy, water being eliminated.

The third acid of the benzoic series, cuminic acid, does not

exhibit this copulative property.

Bertagnini took about 6 grammes of this acid in hourly doses of 0.25 grammes. On the first day there was no inconvenience attending the experiment; on the second day, however, he suffered from continued noises in his ears, and a sensation of being narcotized. The same symptoms occurred in a second experiment, in which about 75 grammes were taken in successive doses. Already, an hour after the injection of the first dose, the urine gave a violet reaction on the addition of salts of iron, a peculiarity which continued during the entire duration of the experiment, and was yet present, though faintly, for forty-eight hours after the last ingestion of salicylic acid. The acid urine was evaporated down to a small bulk, and put aside for crystallization of the salts. The decanted liquid was strongly acidified with hydrochloric acid, and repeatedly digested with ether. The ethereal solutions, on evaporation, left a strongly acid fluid, which, on further evaporation, deposited crystals. These were purified by pressing between paper, recrystallization, and treatment with animal charcoal. The substance so obtained was a mixture of small needles, and large, glistening, needle-shaped crystals, which latter appeared to be volatile on being heated. The separation of the two substances was effected by heating the mixture to from 140° to 150° C. (281° to 302° F.) in a current of air. The volatile body proved to be salicylic acid: the body which remained after recrystallization contained nitrogen, had the composition C1H,ÑO, and the properties of an acid. It dissolved in warm hydrochloric acid, and on cooling crystallized from the solution. By protracted boiling of this solution in hydrochloric acid, it was decomposed, and from the mixture, after neutralization of the hydrochloric acid by means of carbonate of lime in pieces, ether extracted salicylic acid. In solution there remained glycocoll.

9

C,H,O + CHINO,—2HO = = C1H,NO.

6

18

Salicyluric acid.

From the analogy to hippuric acid, Bertagnini was induced to give the name of salicyluric acid to this new copulated acid.