FOOTNOTES:
[34] Recherch. expériment. sur les mouvements des liquides dans les tubes de petits diamètres, Paris, 1828. Comptes rendus t. 19, 1844. Quoted from Hay.
[35] Über die Saftbewegung, 1848.
[36] L’Union Médicale, 1871, Nos. 50 et 52. Gaz. Méd. de Paris, 1879.
[37] Leçons sur les effets des substances toxiques et médicamenteuses, Paris, 1857.
[38] Zeitsch. f. Rationelle Medicin, Bd. I, 1851.
[39] Action of Medicines, 1857.
[40] Archiv f. exp. Path. u. Pharm., Bd. VIII, 1878, S. 355.
[41] Gazette Médicale, 1873.
[42] Journal of Physiology, Vol. XVI, 1882.
[43] Arzneimittellehre, Leipzig, 1883.
[44] Amer. Journ. Physiol., Vol. I, 1898, p. 411.
[45] Loc. cit.
[46] Loc. cit.
[47] Amer. Journ. Physiol., Vol. X, 1904, p. 209.
[48] In all these experiments there was no interval between the emptying of the loop and the beginning of the 10-minute period which followed. The injections were made as rapidly as possible, and in no case occupied more than a minute.
CHAPTER V.
The Inhibiting Action of Calcium and Magnesium on the Movements and Secretion of the Intestine.
It was first observed by Ringer[49] that the unfavorable effect produced by pure NaCl solution could be lessened by adding other salts, notably calcium and potassium. From this observation there was made the so-called Ringer’s solution, which contains Na, K, and Ca in proportions which render the solution relatively neutral and innocuous towards the living tissues.
Howell,[50] working with the heart of the terrapin in various mixtures of Na, K, and Ca chloride, emphasized the importance of calcium in the medium in which the heart beat. He concluded from his experiments that the sodium chloride was mainly instrumental in establishing and maintaining the proper osmotic conditions, while calcium was the main factor in initiating and maintaining the beat of the heart. To quote from his articles:—“The stimulus that leads to a heart contraction is dependent upon the presence of calcium compounds in the liquids of the heart; but for rhythmic contractions and relaxations a certain proportion of potassium compounds is necessary.” “The sodium chloride seems to be essential only in preserving the osmotic relations between the tissues and the surrounding liquid.” Similar conclusions were arrived at by Green.[51]
Loeb,[52] working with Gonionemus, and with the striated muscles of the frog, arrived at conclusions which are in some respects entirely opposed to those of Howell. What Loeb spoke of as the toxic effects of sodium chloride was emphasized by this work. This was especially shown in the case of Fundulus eggs which, though freshly fertilized, cannot develop in pure NaCl solution, although they develop in sea-water or in distilled water. In this case the addition of a small quantity of calcium chloride to the NaCl rendered development possible. According to Loeb, the Ca exerted an antitoxic effect and neutralized the injurious action of the NaCl. Similarly it was found that the apex of the heart contracts rhythmically in a pure NaCl solution, but soon came to a standstill. The addition of a small amount of calcium is sufficient to cause the contractions to persist for a long time. This again was referred to the toxic and antitoxic effects of the salts. From these and similar experiments arose the conception of “physiologically balanced solutions” in which the toxic effect of each substance in the solution is exactly counteracted by the antitoxic effect of some other substance in the same solution.
Other experiments by Loeb showed that if the voluntary muscle of a frog be immersed in a pure NaCl solution, rhythmical twitchings appear which continue for many hours, or even for days. If, however, a small quantity of CaCl2 be added to the NaCl solution the twitchings cease, although the muscle remains alive in this mixture longer than it does in pure NaCl. Similar results were obtained with solutions of the sodium salts which precipitate calcium, fluoride, oxalate, carbonate, phosphate, etc. In all of these solutions twitchings developed in the muscle. Magnesium and strontium act like calcium in inhibiting the muscular twitchings produced by sodium salts. These experiments led Loeb to the conclusion that the presence of calcium in the body keeps the voluntary muscles from constantly twitching or beating rhythmically in the way the heart does. Calcium, magnesium, and strontium seemed to have a definite inhibitory action on the muscular contractions.
Loeb further showed that the center of a jellyfish (Gonionemus), which when isolated from the margin will not contract in sea-water, will beat rhythmically if placed in pure NaCl solution. If a quantity of CaCl2 or Ca(NO3)2 be added to the NaCl solution the contractions are inhibited. Magnesium and strontium behave in this respect like calcium. If also a sufficient quantity of a calcium precipitating solution (sodium fluoride, phosphate, etc.) be added to sea-water in which the center will not beat, rhythmical contractions soon appear, due apparently to the removal of the calcium from the sea-water and the tissue. In these experiments, as in those with voluntary muscles, calcium, magnesium and strontium have apparently an inhibiting action on muscular contractions.
Loeb has recently made experiments on a jellyfish of the Pacific (Polyorchis) with results which are somewhat different from those described for voluntary muscles and Gonionemus. He found that the normal swimming movements of the uninjured animal could not occur in solutions which did not contain some proportion of magnesium, and the presence of magnesium in the sea-water seemed to be the stimulus for the apparently spontaneous movements of the animal. Calcium and potassium were found to oppose this action of magnesium. Further with the isolated center of Polyorchis, which will not beat in pure sugar solution or in sea-water, it was found that the addition of CaCl2, SrCl2, or BaCl2 to either solution caused contractions to appear. Magnesium chloride did not produce this effect. In pure NaCl solution also the isolated center will not beat, or beats only after a long time, while the addition of CaCl2 to the NaCl causes it to beat at once.
Lingle[53] made experiments with the ventricle of the tortoise heart, which was able to beat for only a short time in pure NaCl solutions. When a small amount of CaCl2 is added, however, the heart may continue to beat for a long period. Lingle explained this by the assumption that NaCl is a poison and that calcium acts in an antitoxic way, a suggestion already offered by Loeb.
Loeb’s experiments on the inhibition of muscular twitchings in voluntary muscles by calcium and magnesium, as well as the similar results he obtained with the isolated center of Gonionemus, led me to test the action of these two substances on the rhythmical movements of the mammalian intestine. It was found that not only the normal movements of the intestine, but also those produced by the saline purgatives such as sodium citrate, sulphate, tartrate, etc., could be very definitely inhibited by the administration of calcium or magnesium chloride. This was the case when these latter substances were given in any way either intravenously, subcutaneously, or applied directly to the serous surfaces of the intestine. The following experiments will illustrate this inhibitory action.
A rabbit was anaesthetized by a subcutaneous injection of 4-5 c.c. 1% morphine solution. The intestines were then carefully exposed and protected in every way from loss of heat and moisture. The method suggested by van Braam-Houckgeest[54] of opening the abdomen under the surface of sodium chloride solution is perhaps the most perfect. A small quantity of m/6 sodium citrate solution (for a rabbit weighing 1,200 g. 2-3 c.c. is sufficient) was injected into a vein of the ear. The intestines almost immediately began to move actively. There was then injected 3-4 c.c. m/6 CaCl2 solution. The intestines within 2 or 3 minutes came entirely to rest and remained perfectly quiet. A second injection of a somewhat greater quantity of sodium citrate caused them to again become active.
A still more striking experiment may be made by exposing the intestines and pouring a small quantity of sodium citrate solution on their peritoneal surfaces. Immediately they become extremely active. If now they be washed off with a little NaCl solution and a few c.c. of a solution of calcium chloride be poured on them they will come to rest at once. These solutions must be at body temperature and isotonic with the blood. If the loops which have been quieted by CaCl2 are again moistened with the citrate solution they will be set into motion as before, and a subsequent application of CaCl2 will again cause all movement to cease. This may be continued almost indefinitely. I have set the same loops in motion and stopped them by these solutions as many as sixteen times in succession.
Magnesium chloride acts in this respect like calcium chloride, and a similar but slighter action is possessed by strontium chloride. Magnesium sulphate has a purgative action just as many other sulphates have. Magnesium citrate also acts in the same way as other citrates. The action of the magnesium in these cases seems to be subordinate.
In addition to the inhibitory action of calcium and magnesium on the peristaltic movements of the intestine, these substances also suppress the secretion of fluid into the intestine. This is shown in the previous chapter (IV), where tables are given to show the course of the experiments. According to these experiments, the normal rate of secretion in an isolated loop was measured. The quantity of fluid secreted was small, but the application of CaCl2 or MgCl2 to the serous surface of the loop stopped the secretion entirely. The subsequent application of sodium citrate caused it to flow again.
In its counteraction of the effect of saline purgatives, calcium behaves in the same way. The increased peristalsis or secretion caused by sodium citrate, sulphate, etc., is entirely suppressed by the administration of calcium or magnesium chloride. This is not true to the same extent of those activities produced by barium chloride. CaCl2 as far as I have been able to determine only partially counteracts the effect of BaCl2. That an antagonism does exist cannot be doubted, but the violent peristaltic movements brought about by BaCl2 cannot be fully suppressed by CaCl2 or MgCl2. As mentioned above, BaCl2 in extremely small doses causes an increased flow of urine.[55] This can be partially inhibited by CaCl2. With slightly larger doses of barium, the flow of urine often ceases abruptly, due probably to the contraction of the musculature of the urinary passages, or possibly to a contraction of the blood vessels of the kidney. This condition is relieved by the administration of CaCl2, that is, the calcium merely counteracts the effect of the barium on the musculature of the urinary passages or blood vessels, whichever it may be.
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.
| Time | Salts other than NaCl injected | m/6 NaCl injected in c.c. | Urine in c.c. |
|---|---|---|---|
| 9:25 | |||
| 11:40 | 150 | 64.5 | |
| 11:45 | 10 | 6.6 | |
| 11:50 | 10 | 5.6 | |
| 11:55 | 10 | 6.2 | |
| 12:00 | 10 | 7.4 | |
| 12:05 | 10 | 9.5 | |
| 12:05 | 5 c.c. m/6 CaCl2 | ||
| 12:10 | 5 | 2.2 | |
| 12:15 | 10 | 0.8 | |
| 12:20 | 10 | 1.2 | |
| 12:25 | 10 | 1.6 | |
| 12:30 | 10 | 2.8 | |
| 12:35 | 8 | 3.0 | |
| 12:40 | 5 | 4.5 | |
| 12:45 | 0 | 4.8 | |
| 12:50 | 0 | 5.1 | |
| 12:55 | 0 | 6.2 |
It was found in another series of experiments[58] that the haemoglobinuria caused by saponin and by quillain, which is a dried extract of Quillaja bark, may be inhibited by calcium chloride. The intravenous injection of 2 c.c. ¹⁄₄% quillain always produced haemoglobinuria in a rabbit weighing about 1,200 g. If the dilution of the quillain were made with m/6 CaCl2 instead of water, e.g., 2 c.c. 1% quillain + 6 c.c. m/6 CaCl2 and 2 c.c. of this injected intravenously, no haemoglobinuria resulted, although the concentration of the quillain was the same in both cases. The CaCl2 does not stop the excretion of the haemoglobin by the kidneys, for if the saponin or quillain be given first and the haemoglobinuria established, the subsequent injection of CaCl2 does not stop the excretion of haemoglobin. This is explained by a large number of experiments in which it was shown that the haemolysis caused by saponin, quillain, or digitalin is particularly inhibited by calcium chloride and magnesium chloride. This can be seen in the following table in which defibrinated rabbit’s blood is used, and the effects of CaCl2 and MgCl2 are compared with that of NaCl.
| Time | 1 c.c. blood 5 c.c. m/6 NaCl 3 drops 0.5% saponin | 1 c.c. blood 5 c.c. m/6 MgCl2 3 drops 0.5% saponin | 1 c.c. blood 5 c.c. m/6 CaCl2 3 drops 0.5% saponin |
|---|---|---|---|
| A.M. | |||
| 10:22 | |||
| 10:24 | change of color | no change | no change |
| 10:27 | almost transparent | no change | no change |
| 10:30 | laking almost complete | no change | no change |
| 10:45 | laking complete | no change | no change |
| P.M. | |||
| 1:00 | laking complete | corpuscles settled to bottom; supernatant fluid colored; mixture quite opaque on shaking | same as MgCl2 mixture |
It is of considerable interest to note that these substances, saponin, quillain, and digitalin, act not only as haemolytics, but also as diuretics. This was shown in a number of experiments.[59] As shown in the following table, the injection of a very small quantity of saponin produces a distinct increase in the quantity of urine excreted.
| Time | m/6 NaCl injected intravenously | Urine |
|---|---|---|
| 10:15 | ||
| 10:20 | 10 c.c. | 2 c.c. |
| 10:25 | 20 c.c. | 4 c.c. |
| 10:30 | 20 c.c. | 6 c.c. |
| 10:35 | 10 c.c. | 7.5 c.c. |
| 10:40 | 10 c.c. | 8.0 c.c. |
| 10:45 | 10 c.c. | 8.2 c.c. |
| 10:50 | 10 c.c. | 7.9 c.c. |
| 10:56 | Injected 2 c.c. ¹⁄₂₀% saponin in m/6 NaCl | |
| 11:00 | 10 c.c. | 10.5 c.c. |
| 11:05 | 10 c.c. | 11.0 c.c. |
| 11:10 | 10 c.c. | 11.0 c.c. |
| 11:15 | 10 c.c. | 11.0 c.c. |
| 11:16 | Injected 1 c.c. ¹⁄₂₀% saponin | |
| 11:20 | 10 c.c. | 12.2 c.c. |
| 11:25 | 10 c.c. | 13.2 c.c. |
| 11:30 | 10 c.c. | 12.0 c.c. |
| 11:35 | 10 c.c. | 12.5 c.c. |
It is possible that it is by no means a coincidence that these substances which are powerful haemolytics act also as diuretics; and that CaCl2 and MgCl2, which inhibit the secretion of urine, also to some extent inhibit the haemolytic action. It is difficult to say by what process the haemoglobin is liberated from the red blood corpuscle, as indeed it is difficult to state definitely how fluid passes from the blood into the urine. It is sufficient to call attention to the fact that the liberation of haemoglobin and the flow of urine may be to some extent controlled by the same conditions. If the haemolytics such as saponin cause haemolysis by increasing the permeability of the membranes of the red blood corpuscles, it seems possible that the diuretic effect of these substances may be due to a similar process in the kidney. If this be true, changes in permeability must play an important part in the action of these diuretics. And it is not impossible that the inhibition of the haemolytic action of saponin, etc., as well as the inhibition of the flow of urine by CaCl2 and MgCl2, may be due to a decreased permeability of the red blood corpuscle on the one hand, and of the kidney cells on the other.
With these numerous experiments with calcium and magnesium it is still impossible to make a general statement as to the nature of their action. Since the chemical conditions existing in the tissues of animals and of various parts of animals are largely a matter of conjecture, we cannot predict how these substances will act; nor can we say that because calcium, for example, has a certain action in one animal or on one organ it will necessarily have the same action in other animals or in other organs.
In the experiments on the rabbit’s intestine, however, calcium and magnesium have been shown to have an action which can only be described as inhibitory. In an animal as highly organized as the rabbit, the intestine is an extremely complex organ; it is not only a muscular and a glandular organ, but contains a complicated nervous mechanism peculiar to itself which is entirely inseparable from the other parts. It is not possible here to mechanically isolate a part which shall be free from the nervous system as can be done almost completely in the center of the jellyfish and the apex of the heart. We are dealing with an entire organ which must be considered as an indicator by which comparative results may be obtained. So many unknown conditions exist in such an organ that it is impossible to say what tissue is acted on primarily, whether the nervous system on the one hand, or the glandular and muscular tissues on the other. There are, however, two indicators in the intestine by which the comparative actions of substances can be studied, namely, the muscular movements, and the secretion of fluid, both of which by various chemical substances may be increased or lessened; or, in other words, they may be stimulated or inhibited. These terms are entirely comparative. The fact that calcium and magnesium act as inhibitors for both the muscular and secretory activities of the intestine does not imply that they have a similar action in other organs or in all animals. It can only be said with certainty that the chemical conditions under which the intestines of the rabbit live are fairly constant, so that the addition of calcium or magnesium in some way constantly inhibits the activity of both muscular and glandular tissues, and the addition of certain purgative salts constantly stimulates them to greater activity.