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.