It has not yet been clearly ascertained to which of the constituents of this oil its valuable properties are owing. Being itself an animal product, it is for that reason more easy of assimilation than a vegetable oil. Many have attributed its virtues to Iodine, of which, according to De Jongh, it contains 29 parts in 100,000.
Dr. Theophilus Thompson has tried both Olive and Almond oils in consumptive cases, but has not found that any material benefit is derived from their use. He considers that Cod-oil produces its best effects in cases where Iodine would be inadmissible. Neither does he think its virtue to be due to the biliary matters which it contains, for a mixture of ox-gall with Almond-oil does not supply its place. Cod-oil contains 7½ parts in 100,000 of Phosphorus. Dr. Thompson supposes that its efficacy may be partly owing to this. He has made trial of Phosphuretted Almond-oil, containing one grain of Phosphorus to the pint. He suggests that this Phosphorus may be of use in diverting some of the Oxygen from the tissues. This is to adopt Liebig's theory of the excess of Oxygen in Phthisis; an idea which is not very consistent with the experiments of Dr. Hutchinson on his Spirometer, from which it appears that the quantity of air inhaled at each breath by a consumptive patient is considerably less than in health, on account of a diminished capacity of the lungs. But when a continual fever has set in, an oxidation and waste of the tissues must certainly take place. (Lancet, October, 1851.)
The Phosphorus in Cod-liver oil would soon be oxidized, and it would seem to be too small in amount to be of service in this way. If any thing were thus needed as a pabulum for Oxygen, we might suppose it to be the oil itself that was thus burnt.
Possibly the utility of this medicine may depend upon a combination of several constituents and various properties. It is an oil; and thus of use as an Aliment, and as a supporter of the respiratory function. It is an animal oil; and thus peculiarly adapted for being digested, absorbed and assimilated to the adipose tissues of the human body. It contains Iodine and Bromine, which are useful as Alteratives or blood medicines, both in Phthisis and Scrofula. Their proportion will not seem so small when the large dose of the oil and its frequent repetition are taken into account. But their presence alone would not be sufficient to explain the utility of the oil. It contains also Phosphorus, a general Stimulant, which may prove of use when there is a failure of the nervous forces.
Sometimes the dose of the oil excites a most distressing nausea. This may perhaps be prevented by a judicious modification of the vehicle. It may be floated on an aromatic water, on a bitter infusion, on milk, on wine, or on cold tea, to suit various tastes. In other instances the dose is swallowed without inconvenience, but the patient is not fattened, nor is his condition in the least improved by it. In such incurable conditions it is probable that there is often an organic disease of the Pancreas, or a failure in the function of that gland. For it appears that the absorption of fats is effected by means of an alkali contained in the Pancreatic fluid. When there is reason to suspect this cause of the emaciation, it is advisable to saponify the oil by shaking it with a sufficient quantity of solution of Potash or of Carbonate of Soda. The dose will then be in a state of solution, and ready for absorption.
Cod-liver oil may be used with advantage as a vehicle for Iodide of Iron, in scrofulous cases. Two grains of this may be dissolved in each ounce of the oil. (Vide pp. 119, 191, 229.[47])
SULPHURIC ACID.
Class I. Div. I. Ord. II. Acida.
Class III. Ord. I. Astringentia Mineralia.
This medicine acts chemically as an acid in the blood and in the secretions. When diluted it is easily absorbed, and meeting in the stomach with an acid secretion, it passes into the circulation without being first neutralized. If in small quantity, it is neutralized by the slight excess of alkali in the blood; if in larger amount, it may exceed this alkali, and displace and set free other acids in the blood, combining with their bases on account of its strong affinities. In all cases it increases the quantity of free acid in the system, and tends to render the secretions, as the urine, more acid than they were before. (Vide Dr. Bence Jones's Animal Chemistry, p. 49.)