Experiments have recently been made to test the effect of adding calcium salts to barium chloride and feeding the two mixed with some edible substance to mice. BaCl2 is a common poison to employ for mice and rats. It was found that the mice eating food containing barium carbonate alone died, while those eating the mixture of calcium carbonate and barium carbonate in the food were unharmed.[56]
When loops of the intestine are entirely removed from the body and placed in sodium chloride solution, active movements begin, as will be described in detail in a later chapter. These movements continue 40 to 45 minutes or longer if the proper conditions of temperature, etc., are preserved. If, however, CaCl2 be added to this solution the movements are inhibited. Also loops placed in pure m/6 CaCl2 solution lie perfectly quiet.
A peculiar action of calcium which will be described in detail later on is shown in the following experiments: A loop of rabbit’s intestine was removed from the body and placed in a solution of m/6 LiCl. After moving rhythmically for about 15 seconds the loop came to rest. A loop similarly placed in m/6 CaCl2 solution showed no movements. In a mixture, however, of 50 c.c. m/6 LiCl + 5 c.c. m/6 CaCl2 the initial movements seen in the pure LiCl solution were absent and the loop remained quiet for 10-15 minutes. Then sudden sharp constrictions appear in the loop, followed by violent contractions of the whole loop. The loop twists and coils upon itself and continues to move in this extremely active manner for 30-45 minutes or longer. The control loops in pure LiCl and pure CaCl2 remain motionless during all this time.
A similar phenomenon occurs with a mixture of NaCl and CaCl2. In NaCl, however, the initial movements are much more conspicuous and may continue for an hour. These are inhibited in the mixture of NaCl and CaCl2, and after 10-15 minutes movements of an entirely different character appear, resembling those described for mixtures of LiCl and CaCl2. Sharp constrictions and violent twistings persist for 30 or 40 minutes.
These peculiar contractions do not occur in mixtures of LiCl and NaCl, nor in mixtures of CaCl2 and MgCl2.
In addition to their action on the intestine, calcium and magnesium have a very definite action on other organs of the body, more especially the kidney. It was found[57] that both calcium and magnesium chlorides inhibit the flow of urine. This is shown in the following tables taken from the paper referred to.
Rabbit—cannula placed in bladder. No urine flowed in the first or second periods of 10 minutes before the NaCl solution was injected.
| Time | Salts other than NaCl injected | m/6 NaCl injected in c.c. | Urine in c.c. |
|---|---|---|---|
| 10:10 | 10 | ||
| 10:15 | 10 | ||
| 10:20 | 5 | 0.5 | |
| 10:40 | 10 | 0.8 | |
| 11:00 | 10 | 0.5 | |
| 11:20 | 5 | 1.0 | |
| 11:40 | 10 | 2.8 | |
| 12:00 | 10 | 6.0 | |
| 12:00 | 5 c.c. m/6 CaCl2 intravenously | ||
| 12:05 | 5 c.c. 5m/6 CaCl2 subcutaneously | ||
| 12:20 | 5 | 0.2 | |
| 12:40 | 10 | 1.8 | |
| 1:00 | 10 | 0.8 | |
| 1:00 | 5 c.c. m/6 sodium citrate intravenously | ||
| 1:20 | 10 | 2.2 | |
| 1:40 | 5 | 3.6 |
In this case, although the flow of urine was considerably increased by the injection of NaCl solution, and although the injection was continued, the introduction of CaCl2 caused the flow to almost cease. This action was quite constant and was obtained in a large number of experiments. MgCl2 has a similar but less powerful effect. The action of the CaCl2 is temporary and wears off after a little time, as shown in the following table taken from the same paper. It represents only the latter half of the experiment, the regular injection of 2 c.c. NaCl solution per minute gradually increasing the rate of flow as shown, until the quantity of fluid excreted almost equals that injected.
Rabbit—cannula in bladder—injections intravenous.