FOOTNOTES:
[61] MacCallum, J. B.: University of California Publications, Physiology, Vol. II, 1905, p. 47.
CHAPTER VIII.
The Effect on the Intestine of Intravenous Saline Infusions.
It has been frequently observed that a quantity of fluid enters the intestine during the intravenous injection of normal salt solution. According to Dastre and Loye,[62] the fluid injected into the veins is largely eliminated by the kidneys, although these organs may be assisted in this function by the salivary glands and intestine. These authors have found fluid to be present in the intestine of rabbits as well as in the pleural and peritoneal cavities after the injection of large quantities of salt solution. They state that in such an intravenous injection diarrhœa often results which may be so pronounced that a clear fluid emerges from the rectum. Knoll[63] also mentions the production of diarrhœa by the injection of large quantities of NaCl solution.
Magnus[64] in his work on the production of oedema of the skin by intravenous infusions of salt solutions shows in his tables that a certain amount of fluid is eliminated by the intestines after the kidneys have been removed. A rabbit with both kidneys removed was infused with 1,500 c.c. normal salt solution; 200 g. were eliminated by the intestine. In a second rabbit 1,010 c.c. of fluid were injected into the veins and 60 g. were eliminated by the intestine. In a dog 1,760 c.c. were injected and 160 g. eliminated by the intestine.
I have made a number of experiments[65] in which the amount of fluid passing into the intestine during the intravenous injection of large quantities of NaCl solution was determined not only when the kidneys were removed from the circulation, but also when they were active. As shown by the following experiments, the fluid secreted by the intestine increases rapidly when m/8 or m/6 NaCl solution is injected into the blood. Without such an injection or other stimulus very little intestinal juice can be gathered in a time as short as that occupied by the experiments. In a rabbit’s small intestine there is usually found between 5 and 10 c.c. fluid, often much less.
Exp. 1. Rabbit. The bloodvessels to the kidneys were tied off and two cannulæ were put into the intestine, one 35 cm. from the pylorus and the other in the lower part of the ileum. Each loop was isolated by ligatures. The upper one was about 30 cm. long and the lower one 42 cm. The upper loop in the beginning contained 5 c.c. fluid, which were removed. The lower loop was empty. During the first hour 100 c.c. m/8 NaCl were forced into the blood and 5.2 c.c. fluid appeared in the upper loop and nothing in the lower loop. During the second hour 240 c.c. NaCl solution were injected and 5.4 c.c. fluid appeared in the upper loop and 13.6 c.c. in the lower loop. During the third hour 160 c.c. NaCl solution were introduced; 6.6 c.c. fluid appeared in the upper loop and 15.5 c.c. in the lower. The infusion was then stopped and 26 c.c. were found in the part of the small intestine not included in the loops. The total amount thus secreted by the intestine in three hours was 72.3 c.c. This is 14.46% of the quantity injected.
Exp. 2. In another rabbit with kidneys removed, 470 c.c. NaCl solution were injected during three hours, and 78 c.c. fluid obtained from the intestine, which is about 16.6% of the quantity injected.
Exp. 3. In a rabbit in which the kidneys were left intact, 547 c.c. m/6 NaCl solution were injected into the blood. 49.5 c.c. were secreted in 3 hours and 30 minutes by the intestine. This is about 9% of the total quantity of fluid. The quantity of fluid secreted into the loop in the first half hour was 1.8 c.c.; in the third half hour, 2.9 c.c.; in the fifth half hour, 6.6 c.c.
Exp. 4. In a second rabbit in which the kidneys were untouched, the quantity of m/8 NaCl solution introduced was 390 c.c.; about 40 c.c. of fluid were obtained during three hours from the intestine. This is 10.25% of the amount injected. In the first hour 5 c.c. were secreted into the loop; in the second hour 7 c.c.; and in the third hour 11.1 c.c. In the rest of the small intestine 17 c.c. were found.
It is clear from these experiments that a considerable proportion of the fluid injected in this way is eliminated by the intestine. The quantity is somewhat greater if the kidneys are extirpated. There is, however, a limit to the amount that can be excreted by the intestine, and never, as in the case of the kidney, does the amount excreted approximate the amount injected. The action of such infusions on the intestine is nevertheless quite similar to that on the kidneys, and in many other ways the intestine may be regarded as an excretory organ which can to some extent take on the functions of the kidney. The intestinal juice contains many substances contained by the urine. Among the more conspicuous of these is urea, which was shown by Claude Bernard[66] to be excreted into the intestine as well as the stomach. He found that it is readily broken up in the intestinal juice, so that in many cases only salts of ammonia remain.
Pregl[67] demonstrated the presence of urea in the intestinal juice of the sheep. He found its concentration there to be 0.248%. In the intestinal juice of rabbits I[68] have found that small quantities of urea exist both before and after extirpation of the kidneys. It is present not only in the normal intestinal juice, but also in the fluid obtained from the intestine after the infusion of large quantities of m/6 NaCl. Weintrand[69] has demonstrated uric acid in the intestinal juice.
Secretion of sugar into the intestine. Another instance of the way in which the intestine can to some extent take up the function of the kidney is shown by the secretion of sugar by the gut following the injection of large quantities of normal salt solution. It was shown by Bock and Hoffmann[70] that the injection of 1% NaCl solution into the circulation of a rabbit caused transient glycosuria. Large quantities of the solution were injected at the rate of 25-30 c.c. each 5 minutes, and the glycosuria appeared in from 20 minutes to 1 hour and 30 minutes after the beginning of the infusion. After a number of hours (6-7) the glycosuria diminished in their experiments and finally disappeared, although the infusion of salt and the flow of urine continued. They found that the entire quantity of sugar eliminated was in one case 1.632 g., and in another case 2.04 g. The percentage of sugar in the urine reached 0.136 and 0.219 respectively in the two experiments. These facts were confirmed by Külz,[71] who found also that section of the splanchnics prevented the glycosuria. The experiments lately published by M. H. Fischer[72] show that the glycosuria is caused not only by NaCl, but by certain of the salts which were shown by Loeb[73] to produce muscular twitchings. He further showed that calcium has the power of suppressing the glycosuria.
This secretion of sugar by the kidneys following intravenous infusions, together with the facts shown above that fluid is eliminated to some extent by the intestine in the absence of the kidneys, led me to inquire whether the intestine also secretes sugar when the kidneys have been extirpated and a large amount of NaCl solution is injected. A number of experiments were made to determine this. I have found[74] in brief that with the infusion of large quantities of m/6 NaCl solution into the circulation sugar is abundantly secreted into the intestine. This takes place not only when the kidneys are removed, but also when they are intact, and are also eliminating sugar. This may be seen in the following tables:—
Rabbit—Blood vessels of kidney ligatured; cannula in upper part of small intestine, with loop 35 cm. tied off. Loop emptied; contents 5 c.c., which contained no sugar.
| Time | NaCl m/6 injected | Intestinal juice | Sugar examination of intestinal juice |
|---|---|---|---|
| 10:00 | Infusion begun | Loop emptied, 5 c.c. | No sugar |
| 10:30 | 20 c.c. | 3 c.c. | No sugar |
| 11:00 | 40 c.c. | 3 c.c. | No sugar |
| 11:30 | 20 c.c. | 4 c.c. | No sugar |
| 12:00 | 120 c.c. | 6 c.c. | Trace of sugar |
| 12:30 | 200 c.c. | 12 c.c. | Sugar abundant |
| 1:00 | —c.c. | 28 c.c. | Sugar abundant |
| 400 c.c. |
Here the sugar appeared in the intestinal juice after about 200 c.c. NaCl solution had been injected. The injection was made in each case into the vein of the ear by means of a pressure bottle connected with the water tap. The pressure bottle was in turn connected with a bottle holding the solution, which was thus forced out at a constant rate through a long rubber tube immersed in water at 40° C. A hypodermic needle was fastened in the end of this tube and inserted into the marginal vein of the rabbit’s ear. In this way the quantity of fluid injected could be accurately measured and controlled. The salt solution after passing through the long tube reached the ear at approximately body temperature. It is of the greatest importance to protect the intestinal loops in every way possible from loss of heat or from drying.
In the above experiment the intestinal glycosuria, if such a term may be applied to this phenomenon, appears under circumstances which are exactly the same as those necessary for the production of sugar in the urine by saline infusions. A further example of this is shown in the following experiment:—
Rabbit—Blood vessels of both kidneys ligatured. Intestinal loop including duodenum 32 cm. long. In the loop were found 3 c.c. fluid which contained no sugar.
| Time | NaCl m/6 injected | Intestinal juice | Sugar examination of intestinal juice | |
|---|---|---|---|---|
| 9:45 | Infusion begun | Loop emptied, 3 c.c. | No sugar | |
| 10:15 | 10 c.c. | 3 c.c. | No sugar | |
| 10:45 | 70 c.c. | 3 c.c. | No sugar | |
| 11:15 | 75 c.c. | 3.2 c.c. | No sugar | |
| 11:45 | 85 c.c. | 5 c.c. | Sugar abundant | 0.202% |
| 0.222% | ||||
| 12:15 | 80 c.c. | 9.5 c.c. | Sugar abundant | 0.25% |
| 12:45 | 150 c.c. | 21 c.c. | Sugar abundant | |
| 470 c.c. | ||||
Here the sugar appeared after the infusion of about 240 c.c. NaCl solution. The experiment was not carried on to see how long the sugar would continue to be present in the intestinal juice. The animal was killed, and it was found that the remaining loops of the small intestine held 32 c.c. of fluid which contained sugar. The stomach contents included about 40 c.c. fluid which also contained sugar. Of the 470 c.c. of fluid injected, 78.7 c.c. were eliminated by the small intestine and 40 by the stomach. The alimentary canal, then, exclusive of the large intestine, eliminated about 118 c.c. of the fluid introduced, which is approximately 25%.
Quantitative estimations of the sugar in the intestinal juice in this case were made. The amount varied between 0.2 and 0.3%. I have not attempted to ascertain the total quantity of sugar which may be obtained from the intestinal juice by continued infusion of salt solution. In the case of the urine, Bock and Hoffmann made such determinations and found that the kidney eliminated in one case 1.632 g. and in another case 2.04 g. sugar. M. H. Fischer found that the concentration of sugar in the urine of a rabbit rarely exceeds 0.25% after infusion of m/6 NaCl.
Thus the intestine eliminates sugar in a way that entirely resembles its elimination by the kidneys. The sugar appears in the blood after the infusion of a certain amount of the salt solution and is excreted by the kidney. If the kidneys are removed, it is excreted by the intestine. But even when the kidneys are intact there is a certain amount of sugar excreted by the intestine, just as a part of the fluid injected is eliminated by the intestine when the kidneys are still active. As shown in the following experiment, the sugar appears both in the intestinal juice and in the urine. The quantity of sugar, however, is greater in the urine than in the intestinal juice. In the urine it was found to be about 0.2%, in the intestinal juice considerably less. The quantity of urine also is greater than the quantity of intestinal juice. Therefore the greater proportion of the sugar is excreted by the kidneys.
Rabbit—Cannula placed in bladder. Kidneys intact. Cannula in loop of upper part of small intestine 35 cm. long. Loop contained 4.2 c.c. fluid; no sugar.
| Time. | NaCl m/6 injected. | Intestinal juice. | Urine. | ||
|---|---|---|---|---|---|
| Quantity. | Sugar examination. | Quantity. | Sugar examination. | ||
| 9:45 | Infusion begun. | Loop emp’d, 4.2 c.c. | No sugar. | Bladder emptied, 5 c.c. | No sugar. |
| 10:15 | 5 c.c. | 1.8 c.c. | ” ” | 0.0 | |
| 10:45 | 50 ” | 2.2 ” | ” ” | 0.0 | |
| 11:15 | 80 ” | 2.9 ” | ” ” | 4.0 c.c. | No sugar. |
| 11:45 | 92 ” | 3.8 ” | ” ” | 15.0 | Sugar present. |
| 12:15 | 120 ” | 6.6 ” | Sugar present. | 38.0 | Much sugar. |
| 12:45 | 150 ” | 7.8 ” | ” ” | 40.0 | ” ” |
| 497 ” | |||||
It is interesting to note in connection with these experiments the secretion of sugar into the stomach which followed the intravenous infusion of NaCl solution. Ordinarily in the normal rabbit only a very small quantity of fluid can be obtained from the stomach. This was not found in my experiments to contain sugar. In one case after the infusion of 470 c.c. NaCl solution the stomach contained about 40 c.c. of fluid. In a second instance 32.8 c.c. of fluid were secreted by the stomach during 2 hours and 30 minutes, during which time 390 c.c. NaCl solution were injected. In both these experiments sugar, which was not present in the beginning, appeared in considerable quantities after the infusion had continued for a little time. Thus the stomach excretes sugar under circumstances similar to those under which it is excreted by the intestine. Claude Bernard[75] describes the presence of sugar in the gastric contents of diabetic patients. He quotes McGregor as having made the observation by causing patients to vomit. On examination of the gastric contents sugar was demonstrated. It seems possible that in this case the food might have contained a reducing substance.
Thus a study of the effect of saline infusions on the intestine leads us to the idea of the alimentary canal as in some sense a subsidiary excretory organ. In addition to its other better known functions, the intestine can to some extent take on some of the functions of the kidney. As shown above, it not only tends to eliminate an excess of fluid forced into the circulation, but also excretes urea and uric acid. Further, under circumstances which cause glycosuria, sugar is also excreted by the intestine.