[189]. The ancients considered the urine as a kind of extract of animal substances, a true lixivium, by which every thing impure in the animal economy was washed away, and hence they gave it the name of Lotium.
[190]. Mr. Brande first stated the existence of this acid in urine; but Berzelius expressed his doubts respecting the fact. The experiments of Dr. Marcet, however, are certainty favourable to the conclusion of the former chemist, and Dr. Prout informs us that he has himself seen small calculi discharged from the bladder composed principally of the carbonate of lime.
[191]. The reader will find some interesting observations upon this subject in Dr. Prout’s Treatise, p. 22.
[192]. The name of Uric Acid was suggested by Dr. Pearson: it is, however, as Dr. Marcet very justly remarks, objectionable, on account of the close resemblance which the term bears to that of Urea, a substance totally distinct from Lithic Acid.
[193]. Recherches physiologiques et médicales sur les causes, les symptomes, et le traitement de la gravelle, 8vo. Paris. 1818.
| Ultimate Principles of Lithic Acid. | ||
|---|---|---|
| According to M. Berard, and adopted by M. Majendie. | According to Dr. Prout. | |
| Azote | 39·16 | 31·12 |
| Carbon | 33·61 | 40·00 |
| Oxygen | 18·89 | 26·26 |
| Hydrogen | 8·34 | 2·22 |
| 100·00 | 100·00 | |
[195]. This fact derives its pathological interest from the probability that, in certain states of disease, the Lithic acid assumes this peculiar modification, giving to the sediments of urine those beautiful hues which were formerly considered by Proust, as the effect of an acid, which he named the Rosacic; now as the Purpuric acid, or rather the Purpurate of Ammonia, says Dr. Prout, is nothing more than Lithic acid modified by the action of Nitric acid, and as I have already shewn that the Pink and Lateritious sediments occasionally contain nitric acid in some peculiar state of combination, the nature and origin of the colouring matter cease to be problematical.
[196]. Whence is derived the large quantity of Phosphoric acid which is daily evacuated from the system?—The researches of modern chemistry have furnished a very satisfactory solution of this problem, by demonstrating its presence in those animal and vegetable substances which are used by us as food. Mr. Barry, in prosecuting his interesting and important experiments on the preparation of Pharmaceutical Extracts in vacuo, discovered the curious fact, that Phosphoric acid is to be found in all the extracts in a soluble state; and on extending the investigation, says he, it was ascertained that this acid, besides that portion of it which exists as phosphate of lime, is contained in a vast variety of vegetables, and more especially in those which are cultivated. Medico-Chirug. Trans. Vol. 10, p. 240.
[197]. The urine of infants and nurses contains very little phosphate of lime and phosphoric acid; it is not until after ossification is finished, that these elements are found in abundance in the urinary fluid. That of old men, on the contrary, contains a great quantity of them; the bony system, already overcharged with phosphate of lime, refuses to admit more of it. This saline substance would ossify every part, as it does sometimes in the arteries, ligaments, cartilages, and membranes, if the urine were not to remove the greater part of this superabundant portion. In Rachitis it is by the urine that the phosphate of lime passes off, the absence of which causes the softness of bones. (Richerand). If we might be allowed to theorise, I should say, that this disease depends upon a deficient action in the powers of assimilation, in consequence of which the phosphoric acid is incapable of entering into its assigned combinations, and is therefore eliminated as excrementitious. Dr. Glisson considered the disease to depend upon some fault in the spinal marrow, whence he termed it Rachitis, from ῥακὶς Spina Dorsi.