The results of a number of these experiments may be observed in the following table:—
| No. | Salt | Concentration of Solution | Time | Length of loop | Muscular movements and duration | Secretion of fluid |
|---|---|---|---|---|---|---|
| 1 | NaCl | m/8 | 40 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 | Na2SO4 | m/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. |
| 10 | NaCl | m/8-70 c.c. | 20 ” | 25 ” | Active mov’m’ts. | 0.6 c.c. clear yellow fluid. |
| BaCl2 | m/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. |
| 14 | NaCl | 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. | |||
| 15 | BaCl2 | m/8-50 c.c. | 1st 20 min. | 32 ” | Violent contractions. | 2.7 c.c. |
| 2nd 20 min. | 0.2 c.c. | |||||
| 16 | NaCl | m/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 ” | None | None |
| 18 | ” | ” | 20 ” | 15 ” | ” | ” |
| 19 | CaCl2 | m/8-50 c.c. | 20 ” | 10 ” | ” | ” |
| NaCl | m/8-50 c.c. | |||||
| 20 | CaCl2 | m/2-50 c.c. | 20 ” | 15 ” | Slight movements not peristaltic in character. | ” |
| NaCl | m/2-50 c.c. | |||||
| 21 | CaCl2 | m/1-50 c.c. | 20 ” | 15 ” | Slight movements not peristaltic in character. | Slight trace. |
| NaCl | m/1-50 c.c. | |||||
| 22 | NaCl | m/8-30 c.c. | 20 ” | 35 ” | Irregular contractions, not strong | None. |
| BaCl2 | m/8-1 c.c. | |||||
| CaCl2 | m/8-30 c.c. | |||||
| 23 | NaCl | m/8-30 c.c. | 20 ” | 30 ” | Irregular contractions, not strong | 0.2 c.c. |
| BaCl2 | m/8-1 c.c. | |||||
| CaCl2 | m/8-30 c.c. | |||||
| 24 | BaCl2 | 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.
FOOTNOTES:
[60] MacCallum, J. B.: University of California Publications, Physiology, Vol. I, 1904, p. 115.
CHAPTER VII.
The Action on the Intestine of Solutions Containing Two Salts.
As stated above, it was shown by Claude Bernard and by Pflüger that section of the spinal cord below the phrenic nerve, or section of the splanchnic nerves, causes a marked increase in the intestinal movements, and also an increase in the amount of fluid secreted (Moreau). These movements continue in loops isolated and removed from the body and placed in m/6 NaCl, LiCl, Na2SO4, sodium citrate, etc., for varying periods of time. They continue far longer in NaCl than in any other solution. Calcium chloride inhibits these movements, as is the case also with magnesium chloride. It was found,[61] however, in making these experiments with isolated loops removed from the body, that with certain mixtures of NaCl or LiCl with CaCl2 or MgCl2, movements began after 20 or 25 minutes of a character differing entirely from the movements seen in pure NaCl. An idea of this phenomenon may be gained from the following description of experiments.