This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
1 T. Lauder Brunton and Pye-Smith on 'Intestinal Secretion and Movement,' British Association Reports, 1874, 1875, 1876.
In order to simplify the problem presented by the complicated nervous arrangement in the intestine, Ludwig and Salvioli have used the plan of keeping up the circulation artificially in a small piece of intestine, and then investigating its movements under various conditions. The intestine was laid on a piece of cork, in a warm chamber. It was supplied with blood by means of a cannula placed in the artery, and allowed to flow out through a cannula in the veins (Fig. 132). Its movements were registered by a small lever placed upon it. When blood fully oxygenated passed through it, the lever traced only a straight line or gently oscillating curve (Fig. 134), but when the flow of blood was stopped, so that the blood stagnated and became venous, contractions began which were indicated as a series of curves. A trace of peptone caused first strong contraction and then a number of irregular contractions, at the same time that the vessels became fuller of blood (Fig. 134). Nicotine causes brisker movements of the intestine, and lessens the rapidity of the flow of blood (Fig. 135). In large doses it causes tetanic contraction of the circular fibres.
Fig. 132. - Diagrammatic representation of apparatus for testing the action of drugs on the intestine by artificial circulation through it. For the sake of simplicity the means employed to keep up the temperature of the intestine and apparatus have been omitted. A, a board on which the intestine, b, is laid, c, a cannula tied into a branch of the mesenteric artery, d, d, two stopcocks, by means of which pure blood or poisoned blood may be passed at will through the cannula. e and f, two flasks containing pure and poisoned blood. g, a block on which they stand, and by which they can be raised to a greater or less height, so as to alter the pressure under which the blood flows. When the apparatus is kept warm the pressure is more easily regulated by passing air into the flasks from a pressure bottle. h, the lever for registering the movements of the intestine. One end is weighted and rests on the intestine, I is the axis on which the lever works. k is a revolving cylinder on which the movements are recorded.
Fig. 133. - Shows the effect of anaemia. The upper tracing shows the movements of the intestine supplied with normal blood; the lower shows the movements of an intestine rendered more vigorous by anaemia.
Fig. 134. - Shows the effect of peptones. The first half of the tracing shows the movements of an intestine supplied with blood thoroughly oxygenated; the second half shows the effect of blood containing peptones.
FiG. 135. - Shows the effect of nicotine. The part of the tracing marked A B shows the intestinal movements during the circulation of blood saturated with oxygen (apnoeicblood); the part N B of blood containing nicotine.
Fig. 136. - Shows the effect of opium. In the first part of the tracing the intestine was supplied with apnoeic blood; in the latter with blood containing opium.
Atropine causes irritation of the vessels, while the muscular fibres remain at rest. The action of opium is very remarkable; when the tincture is added in the proportion of .04 to .01 per cent. to the blood which is circulating through the intestine, the circulation becomes at once lessened, but almost immediately afterwards the diminution passes abruptly into great increase, so that five or seven times as much blood flows through in a given time as formerly; at the same time all the movements of the intestine are abolished, but the intestinal wall instead of being relaxed, as one would expect, is in a condition of considerable contraction (Fig. 136). When the opium is washed out of the vessels by pure blood, the after-effects vary according to the quantity which is used. If it is small, the movements and circulation in the intestine soon become normal, but if a large dose has been used, the circulation returns to the normal condition, but the movements remain abolished for a length of time. The peristaltic action induced by nicotine is arrested by opium. The local action of this drug therefore seems to be that it converts the peristaltic movement into a steady contraction.
A remarkable difference between the action of salts of sodium and potassium on the intestine has been detected by Nothnagel,1 and his results have been confirmed by Fioel. When the intestine is exposed, and a potassium salt is applied to its external or peritoneal surface, it produces a contraction of the muscular walls, which remains localised to the point of contact, or simply causes a ring of contraction opposite the point (Fig. 137a). When a sodium salt is used instead, it produces a contraction which is not limited to the point of contact, but always spreads some little distance from it, and sometimes does so in the direction towards the pylorus, and not towards the anus (Fig. 137 b), but at other times spreads equally in an upward and downward direction2 (Fig. 138 a). This peculiar action appears to be due to the potassium salts acting as stronger muscular irritants than the sodium salts, while the progressive contraction caused by the sodium is due to the intestinal nerves in their case being to a greater extent involved.