[24] It is stated by Dr. Carpenter, that if a ligature be applied below the pylorus of an animal, and Sulphate of Magnesia then introduced into the stomach, purging is produced. This could only be by the absorption of the salt, and its subsequent action from within on the mucous membrane of the bowel below the ligature. This experiment is unauthenticated, but if verified would certainly be most conclusive in favour of the view adopted above.
[25] Hydrochloric acid would probably precipitate medicinal solutions containing silver, and thus render this substance inert when given internally. Another therapeutic argument against this, as the acid of the gastric secretion, may be drawn from the fact that the action of calomel is very different from that of bichloride of mercury,—whereas this acid would convert the former into the latter.
[26] Liebig (Animal Chemistry, Part I. p. 76) states that the Bile contains Carbonate of Soda. The assertion that the Pancreatic juice is alkaline must be rested mainly on the authority of M. Bernard.
[27] Occasionally, as in certain cases of Pyrosis, slight vomiting may take place without any straining effort of this kind, but apparently from the contraction of the stomach alone.
[28] Pereira's Materia Medica, 2d edit., vol. ii. pp. 1496, 1507, and elsewhere.
[29] Irritant Cathartics, like irritant emetics, may sometimes affect remote parts on the principle of counter-irritation. Some explain in this way the use of purgatives in disorders of the brain, but there are other reasons which serve to account for this still more satisfactorily. (Vide Chap. IV., Art. Purgatives.)
[30] The process of cure by counter-irritation may be ascribed to the secondary action of some medicines. Such an operation may take place at a distance from the part affected; but it is attributable to a peculiar affection of the nervous system, and has no necessary connexion with the primary or proper action of a medicine. Vide p. 67.
[31] The details of this arrangement are founded solely upon the therapeutic operation of medicines, as used to cure diseases, and not in any way upon their physiological action upon a healthy man. Much unnecessary confusion, in works on Materia Medica, has arisen from these two different matters being taken into account at the same time. Food is the only restoration of wanting material needful to a healthy man; neither is there in such a case any need or opportunity for the counteraction of morbid agencies.
[32] Animal Chemistry, p. 20.
[33] Possibly some parts of the bile, besides the colouring matter, are truly excrementitious. But part of it is needful in the animal economy, as has been proved by experiment. M. Schwann found that when the contents of the bile-duct in dogs were caused to discharge themselves externally through a fistulous opening in the wall of the abdomen, the animals quickly wasted away and died. In some cases of jaundice, the constituents of the bile appear to be vicariously excreted by the kidneys; and perhaps the great depression produced by that disorder maybe partly accounted for by the impossibility of the re-absorption into the blood of these substances, naturally formed by the liver. Having passed into the urine, there is no provision to enable them to return.