FOOTNOTES:

[49] Journal of Physiology, Vols. 4, 5, 6, 8, 16, 17, and 18, 1883-1895.

[50] Amer. Journ. Physiol., Vol. 2, 1898, p. 47.

[51] Amer. Journ. Physiol., Vol. 2, 1898, p. 82.

[52] Festschrift f. Fick, 1899. Chicago Decennial Publications, 1902, and Pflüger’s Archiv, Bd. 91, S. 248, 1902. Amer. Journ. Physiol., Vol. 5, 1901.

[53] Amer. Journ. Physiol., Vol. 4, p. 265, 1900; Vol. 8, p. 75, 1902.

[54] Pflüger’s Archiv, Bd. 6, 1872; and Bd. 8, 1874.

[55] MacCallum, J. B.: Journal exp. Zoology, No. 1, 1905.

[56] Stover, F. H.: Bulletin of Bussey Institution, Vol. II, Part IV, 1884.

[57] MacCallum, J. B.: Journal Exp. Zoology, Vol. I, No. 1, 1904.

[58] MacCallum, J. B.: University of California Publications, Physiology, Vol. II, 1905, p. 93.

[59] MacCallum, J. B.: Loc. cit.

CHAPTER VI.
The Action of Saline Solutions on Loops of Intestine Removed from the Body.

The fact shown above that local application of saline solutions to the peritoneal surfaces of the intestine could call forth not only muscular movements of the intestine, but also an increased secretion, suggested the possibility of experimenting with loops of intestine entirely removed from the body. Loops thus isolated are necessarily placed under new conditions differing entirely from those under which loops normally connected exist. As mentioned in an early chapter, it was stated by Claude Bernard that section of the spinal cord below the phrenic causes active movements to appear in the intestine; and it was later shown by Pflüger that section of the splanchnic nerves has the same effect, and stimulation of the peripheral cut ends caused the movements to cease. It was also noticed by van Braam-Houckgeest that although loops of the intestine normally connected in the body remained at rest when immersed in isotonic NaCl solution, active movements appear in the loops when the splanchnic nerves are cut. Moreau further showed that section of the mesenteric nerves causes a large increase in the fluid secreted into the intestine.

I have confirmed these results and have found that loops which are quiet when the abdomen is opened remain quiet when placed in m/6 NaCl solution. If, however, loops have become active in any way, through exposure to the air, or through any stimulation, these movements continue when the loops are placed in the salt solution. In any case section of the cervical cord or of the splanchnic nerves, or clamping of the nerves and bloodvessels supplying the loops, causes a very marked increase in the peristaltic activity of the loops. In studying the behavior of isolated loops removed from the body and placed in various solutions it was therefore necessary to consider the effects produced by the removal itself.

In describing these experiments, which were made some time ago,[60] a word may be said as to the methods employed. The rabbits were anaesthetized with morphine as described before; the abdominal cavity was opened and the bloodvessels supplying the loop selected were carefully tied off. Two pairs of ligatures were then placed around the intestine so that the loop was properly isolated. The intestine was then cut between each pair of ligatures, and the mesentery divided between the bloodvessel ligatures and the intestine. In this way the loop could be taken from the body without injuring it, and without causing the animal to lose more than a drop or two of blood. The loop was then emptied by cutting one ligature and allowing the fluid to drain from that end while it was held up by the ligature of the other end. The open end was then religatured, and the whole loop suspended in the solution to be tested. This was arranged so that both ends of the loop were above the surface of the solution, in order that none of the solution could by any possibility enter the lumen of the loop through the ligatured ends. The beakers containing the solutions were kept in a water bath at 39.5° C. The movements of the loops could in this way be directly watched, and the amount of fluid secreted in a unit of time could be easily measured.

If a loop such as has been described above be removed from the intestine of a rabbit and placed in m/8-m/6 NaCl solution at body temperature, active movements at once appear. These are regular and rhythmical, resembling those which set in when the nerves to the intestine are cut in the uninjured animal. If the loop be allowed to lie at the bottom of the solution, it will twist and writhe about in a peculiar worm-like manner. These movements persist in varying intensity for a considerable time, sometimes as long as an hour, usually for 40-45 minutes. They disappear gradually. No attempt was made to obtain a fluid in which the movements could be maintained for a longer time. These movements are probably merely the continuation of those always caused by sectioning the nerves to the loop. The m/6 or m/8 NaCl solution seems to be fairly favorable for their maintenance. That the loop, however, is not dead when the movements in NaCl cease is shown by the fact that it can be caused to exhibit active movements by transferring it to a solution of NaCl containing a small quantity of BaCl2. It is of course not possible to say that the movements which appear when the loop is placed in pure NaCl solution are entirely due to the cutting of the nerves to the loop. It is possible that the NaCl acts as a direct stimulus and causes the movements to continue.

When a loop is carefully emptied and suspended in a solution of m/8-m/6 NaCl in the way described, it is found that after a considerable time (20-40 minutes) it is still quite empty. If, on the other hand, an m/2 solution of NaCl is used the loop is found to contain after 15 to 20 minutes a small but distinct quantity of clear yellowish fluid resembling the normal intestinal juice. A loop 27 cm. long suspended in m/2 NaCl for 20 minutes contained 0.6 c.c. fluid. A second loop 30 cm. long in the same solution contained 0.8 c.c. fluid. A control loop of the same length in m/8 NaCl remained empty. In m/2 NaCl the movements of the loop are spasmodic and the contractions very strong. The movements do not usually last more than 5 minutes, although the loop may be removed from this solution 15 minutes after the movements have ceased, and may be caused to move again by immersing it in m/8 NaCl containing ¹⁄₂₅ of its volume of m/8 BaCl2. This shows that the loop is not actually killed by the strong NaCl solution.

A loop suspended in m/6 sodium citrate solution showed active peristaltic movements, lasting for 20 to 30 minutes. No fluid, however, collected in this loop. When suspended, however, in m/2 sodium citrate a measurable quantity of fluid was obtained after 20 minutes. A similar result was obtained with Na2SO4, active peristalsis, but no secretion being caused in an m/6 solution. In an m/2 solution, however, a considerable quantity of fluid collected in the loop.

A loop 28 cm. long suspended in m/8 NaF exhibited active peristaltic movements which continued for less than 10 minutes. At the end of 20 minutes the loop was found to contain 0.8 c.c. of a clear but slightly blood-stained fluid.

Loops suspended in m/6 NaCl containing m/6 or m/8 BaCl2 in the proportion of 50 to 1 or 70 to 1 showed very strong muscular contractions and a well marked secretion of fluid. The muscular movements were characteristic of barium. Violent local contractions and firm constrictions of the intestine together with strong peristaltic movements took place. The loops always contained a distinct and measurable quantity of fluid after being suspended in this fluid, as may be seen in the table which follows.

Loops placed in m/6 CaCl2 showed no muscular movements whatever, nor did any fluid gather in the lumen. This is in marked contrast to the behavior of the loops in the solutions already described. In equal parts of m/6 NaCl and m/6 CaCl2 no movements or secretion took place.

The results of a number of these experiments may be observed in the following table:—

No.SaltConcentration of SolutionTimeLength of loopMuscular movements and durationSecretion of fluid
1NaClm/840 min.30 cm.Active peristalsis 40 min.0.0
2 ” ” 20 ” 23 ”Active peristalsis 40 min.0.0
3 ” m/2 20 ” 30 ”Strong contractions 5 min.0.8 c.c. clear yellow fluid.
4 ” ” 20 ” 30 ” Strong contractions 5 min.0.6 c.c. clear yellow fluid.
5 Sod. Cit. m/8 20 ” 20 ”Active peristalsis 20 min.0.0
6 ” m/2 20 ” 32 ”Violent contractions 2-3 min.0.4 c.c. clear yellow fluid.
7 Na2SO4m/8 20 ” 33 ”Active peristalsis.0.0
8 ” m/2 20 ” 30 ” Strong contractions of short duration.1.5 c.c. clear yellow fluid.
9 NaF m/8 20 ” 28 ” Strong contractions 10 min.0.8 c.c. slightly bloody.
10NaCl m/8-70 c.c.20 ” 25 ”Active mov’m’ts. 0.6 c.c. clear yellow fluid.
BaCl2m/8-1 c.c.
11 ” ” 20 ” 46 ”Active mov’m’ts. 0.8 c.c.
12 ” ” 20 ” 60 ”Active mov’m’ts. 1.2 c.c.
13 ” ” 20 ” 31 ”Active mov’m’ts. 1.2 c.c.
14NaCl m/8-50 c.c.1st 20 min.63 ”Active mov’m’ts. 1.6 c.c.
BaCl2 m/8-1 c.c. 2nd 20 ”0.2 c.c.
15BaCl2 m/8-50 c.c.1st 20 min.32 ”Violent contractions.2.7 c.c.
2nd 20 min.0.2 c.c.
16NaClm/8-30 c.c.20 min. 23 ” Violent contractions.0.9 c.c.
BaCl2 m/8-30 c.c.
17 CaCl2 m/8 20 ” 20 ” NoneNone
18 ” ” 20 ” 15 ” ” ”
19CaCl2 m/8-50 c.c.20 ” 10 ” ” ”
NaClm/8-50 c.c.
20CaCl2 m/2-50 c.c.20 ” 15 ”Slight movements not peristaltic in character. ”
NaClm/2-50 c.c.
21CaCl2 m/1-50 c.c.20 ” 15 ”Slight movements not peristaltic in character.Slight trace.
NaClm/1-50 c.c.
22NaCl m/8-30 c.c.20 ” 35 ”Irregular contractions, not strongNone.
BaCl2 m/8-1 c.c.
CaCl2 m/8-30 c.c.
23NaClm/8-30 c.c.20 ” 30 ”Irregular contractions, not strong0.2 c.c.
BaCl2 m/8-1 c.c.
CaCl2 m/8-30 c.c.
24BaCl2 m/8-1 c.c.20 ” 30 ”Irregular contractions.0.2 c.c.
CaCl2 m/8-50 c.c.

It is interesting to note again here that the secretion into these loops is almost uniformly inhibited by the presence of calcium. When barium is also present in the solution this inhibition is only partial. The action of barium is never entirely counteracted by calcium chloride.

The experiments further show that the saline purgatives act on the intestine not only when it has its normal position and connections with the rest of the body, but also when it is entirely isolated. This eliminates in the first place the possibility of the solutions acting entirely through the central nervous system. It is possible that the salts have some influence on the central nervous system, but from these experiments it seems probable that their main action is either on the glandular and muscular tissues themselves, or on the plexuses of Auerbach and Meissner in the intestinal walls.

As I have already shown, the action of a saline purgative on the intestine consists of two parts, the increase of the peristaltic activity and the increase of the amount of fluid secreted into the lumen; or, in other words, the action on the muscle and the action on the glandular tissue. In the experiments just described it is clear that these two separate actions exist side by side. For example, m/8 solutions of sodium chloride, citrate, or sulphate cause well marked peristaltic movements or allow these to continue, while no secretion of fluid takes place. Stronger solutions of these salts, on the other hand, such as m/2 produce a distinct secretion. Thus a concentration of a salt which is sufficient to produce muscular activity may not be sufficient to affect the glandular tissues. One is tempted to conclude that in the intestine it requires a stronger stimulus to produce secretory activity than it does to cause muscular movements. It is possible that this is true, but the anatomical relations also must be taken into consideration. The muscle coats lie immediately under the thin peritoneal layer through which the salts are absorbed; and it seems probable that in the experiments described the solutions reached the muscle more easily and rapidly than they could the glandular tissue which is situated on the other side of the muscular and submucous layers. Further, it must be noticed that the movements seen in m/8 NaCl may be merely the continuation of those caused by separation of the loop from the central nervous system.

The amount of fluid which may be secreted by a loop of intestine isolated from the body is limited by the absence of the blood supply. The loop, as shown above, secretes a certain amount of fluid in the first 10 or 20 minutes. If it is then emptied, usually no more fluid appears. The quantity secreted depends on the amount of fluid contained in the intestinal walls at the time of its removal from the body. No fluid passes from the solution in which the loop is suspended into the lumen of the loop; no current is established through the walls from the outside inwards. It seems possible to supply the stimulus for secretion in the solution in which the loop is suspended; but it is not possible in this way to renew the fluid which the glands have secreted into the lumen. This can apparently be done only through the blood vessels.