Part 18

A discussion of some further medical questions may here be taken up. The first concerns the therapeutic use of the neutral and alkaline salts of sodium. In clinical, pharmacological, and physiological text-books it is stated now, as ever, that these salts promote a flow of gastric juice. We may look in vain, however, for any experimental foundation to support this doctrine. The experiments brought forward cannot be regarded as conclusive. When Blondlot sprinkled sodium bicarbonate upon flesh, or Braun and Grützner introduced sodium chloride solutions directly into the blood, they began with methods either false in themselves or far removed from normal conditions. In this case, however, the gaps in the experiment were happily made good by the clinician, for the experiment appeared to be confirmatory of clinical experience. That sodium salts (the chloride and bicarbonate) are useful in disorders of the digestive apparatus there can be no doubt. How do they act, however? It appears to me that here, as in some other cases, medical science has fallen into error. When we know that an effect takes place it does not by any means imply that we know the mechanism by which it occurs; and although medicine is broad enough and comprehensive enough to make free use of empiricism in practice, yet it often thinks in narrow grooves when it turns to the explanation of facts. It frequently tries to explain complicated healing processes in the simplest way, on supposed physiological data. And this is true in the present case, which affords an example of prevalent medical reasoning; the alkalies work favourably in digestive disturbances--therefore they are succagogues. Naturally the stomach, under the influence of alkalies, sometimes begins to secrete a greater quantity of juice. This means, however, that it has recovered from a disordered state and has returned to normal conditions. Consequently, the effect is due to the fact of recovery, and not to a direct influence of the alkalies. This latter, however, must be specially proved. The assistance afforded by the alkalies to the organism might be capable of another explanation; for example, that which is ordinarily given. In this case, however, I venture to offer a reason for the effects of sodium chloride, and of the alkaline salts of sodium, which is exactly the opposite of that generally accepted. We were unable to convince ourselves of any succagogue influence on the part of these salts. Indeed, both on the stomach and pancreas they proved in our hands to have an inhibitory effect. In addition to the experiments which I previously brought forward concerning the relation of alkalies to gastric and pancreatic juice, I may relate the following observation. A dog which fortunately had survived the performance, one after the other, of a gastric fistula, a pancreatic fistula, and an œsophagotomy, received daily during the course of several weeks an addition of soda to its food. The animal enjoyed good health and had an excellent appetite. When the first sham feeding experiment was carried out, the relatively small effect of this otherwise very active juice-exciting procedure at once struck us. At the same time we observed that the pieces of flesh which fell from the upper end of the œsophagus, contrary to the ordinary rule, were hardly at all insalivated. In this dog, therefore, a greatly lowered activity of several digestive glands--viz., of the gastric, pancreatic, and salivary glands--simultaneously existed. With regard to the salivary glands the circumstance was naturally submitted to closer investigation. I believe that the inhibitory influence of the alkalies on the digestive glands, which was here proved experimentally, may furnish a basis for the following representation of their mode of action in producing healing effects. Catarrhal affections of the stomach are characterised by an incessant or very protracted secretion of slimy, weakly acid gastric juice. Further, in many cases the affection begins with a hypersecretion, that is an abnormal excitability, of the secretory apparatus which makes itself evident in a superfluous and useless flow. The same must be conceived to happen in disorders of the pancreatic gland; at least such a condition sets in after operations performed for physiological purposes. It is, further, justifiable to suppose that, when an affection is once set up by this or that cause, it may later maintain itself independently; for continuous activity has undoubtedly a harmful influence on the glands. The due nourishment, and the restoration of organs after

## activity, proceeds best during rest. In the normal course of events,

after a period of active work follows a pause, during which the latent work of restoration is accomplished. When, therefore, a remedy effectively restrains the excessive work of a diseased organ, it may in this way contribute to the removal of the pathological condition, and thus to a restoration of the normal state. In this consists, in my opinion, the healing effects of the alkalies. One might draw a parallel between the action of these substances in digestive disturbances and that of digitalis in compensatory disturbances of the heart. An uncompensated heart beats rapidly, and thereby only aggravates its condition. Its time of rest, that is of recovery, of restitution of the organ, is shortened. A vicious cycle is set up. The weak action of the heart lowers blood pressure; the lowering of this leads (from known physiological causes) to an increase in the number of beats; the quickening leads to weakening of the organ. Without doubt the digitalis aids by breaking through this vicious cycle, in that it greatly slows the pulse, and thereby gives new power to the heart. With our explanation of the action of the alkalies harmonises the further circumstance that, with the use of the salts in question, a strict diet is generally prescribed, which means that a certain amount of rest is secured for the digestive glands. It is interesting that in clinical investigations with the stomach-tube, after a period when the alkalies were looked upon as succagogues, a new phase has also set in, mention being now more frequently made of a restraining effect.

The cause of the erroneous belief that alkalies promote a flow of juice obviously lies in this, that people omitted to compare the effects of the saline solutions with those of like quantities of water (_Dr. Chigin_).

The second point which we may consider is the following. The chief difficulty of the physician who wishes to regulate the diet of patients when they suffer from digestive disturbances consists in the fact that idiosyncrasy plays a very important _rôle_. In one and the same illness, different patients react to the same diet in wholly different ways. That which is agreeable to one, and is well borne and useful, may be rank poison to another. Consequently, the golden rule in dietetics is to give no directions with regard to food till one has made inquiries concerning the inclinations and habits of the patient. What does all this indicate? Till now physiology had no experimental answer to the question. But our facts, it appears to me, contribute to a clearing up of the situation. Every food determines a certain amount of digestive work, and when a given dietary is long continued, definite and fixed types of glands are set up which can only slowly and with difficulty be altered. In consequence, digestive disturbances are often instituted if a change be suddenly made from one dietetic _régime_ to another, especially from a sparse to a rich diet; such, for instance, as happens after the long Russian fasts. These disturbances are expressions of the temporary insufficiency of the digestive glands to meet the new demands made upon them.

Finally, it may be of some use to relate the following here. There are often cases of sudden and unaccountable digestive disturbances. From the standpoint of modern physiology they might be explained by an activity of the secreto-inhibitory nervous system, which from some cause or other has been excessively and abnormally stimulated. In any case this system is now a factor of which the physician has to take due account.

SWALLOWING AND MOVEMENTS OF THE STOMACH AND INTESTINES

BY W. B. CANNON, M.D.

_Of the Physiological Laboratory of the Harvard Medical School Boston, Mass., U. S. A._

[NOTE.--In the beginning of 1896 Dr. Professor Henry Pickering Bowditch, one of our Board of Scientific Assessors in the Nutrition Case suggested the use of the Röntgen ray as a means of learning more than was then known about the mechanism of swallowing. There was much difference of opinion among research physiologists about this important function, and the question was far from settled. Magendie published a theory of deglutition, in Paris, in 1836, which was practically accepted until 1876, when Dr. Professor Angelo Mosso, of the University of Turin, Turin, Italy, established the theory of sole peristaltic assistance in swallowing. Again in 1880 Dr. Professor Kronecker, of Berne, Switzerland, in connection with Dr. Falk, and later in connection with Dr. Meltzer, of New York, produced evidence to prove a more complicated process in deglutition than that of peristalsis alone. But even Kronecker and Meltzer found, as they went on, evidence to modify their earlier beliefs, and hence the subject was not cleared up to a point of general agreement.

The suggestion made by Dr. Bowditch was taken up in the Harvard Physiological Laboratory and formed the beginning of a series of studies of the mechanical factors in digestion. The reports of these studies, presented by Dr. W. B. Cannon and collaborators, in the _American Journal of Physiology_, in the volumes of 1898 and 1903, are so understandable, even to the layman ignorant of physiological nomenclature, that we are prompted to give them, almost entire, leaving out only the technical description of the methods employed, which are only interesting to research students who have access to the _Journal_.

It will be noted that three of the professors of physiology mentioned in connection with this preliminary study of the nutrition problem--Bowditch, Mosso, and Kronecker--are members of our presently organised Board.—HORACE FLETCHER.]

THE MOVEMENTS OF THE FOOD IN THE ŒSOPHAGUS

BY W. B. CANNON AND A. MOSER

_From the Laboratory of Physiology in the Harvard Medical School_

Extracts from _American Journal of Physiology_, 1898

The movements of deglutition, in common with many other physiological processes, were explained by the older physiologists on anatomical grounds. Thus, Magendie divided the act into three parts, corresponding to the anatomical regions of the mouth, pharynx, and œsophagus. The muscles of each of these divisions were considered the active agents in propelling the food onward. The function of moving the mass to the pharynx was variously ascribed to the tongue itself, to the mylohyoid muscles, and to gravity. For the second part, the movement through the pharynx, there was more unanimity of opinion, since the constrictors, especially the middle and lower, were evidently concerned.

Direct observations on the movement of swallowed masses in the œsophagus were first made by Mosso. The œsophagus of a dog was laid bare, and a transverse incision made through it, or a piece of it excised. A small wooden ball was placed in the canal below the excised part, and the animal was then stimulated to swallow. One or two seconds after the contraction of the pharyngeal muscles a peristaltic wave began to traverse the œsophagus. This wave did not stop at the point of excision, but in due time reappeared below, and carried the ball to the stomach. Thus the act was shown to be controlled by the central nervous system. Peristalsis was so plainly the motive power that the action was never doubted. Yet this belief was soon to be questioned.

In 1880 Falk and Kronecker studied the movements in the mouth and pharynx, and advanced the theory that deglutition was accomplished by the rapid contraction of the muscles of the mouth. During the act of swallowing the air-tight buccal cavity shows a manometric pressure of twenty centimetres of water. The same pressure was demonstrated to be present also in the œsophagus, but not in the stomach. This pressure was considered sufficient to force food through the œsophagus before the peristaltic wave traversed it. Another argument for rapid descent was found in the fact that cold water can be felt in the epigastric region almost immediately after being swallowed. Further, when strong acids pass through the gullet, they corrode but small parts of it, and not the entire mucous membrane, as would be the case were the acid carried to the stomach by peristalsis.

Over a year and a half ago it was suggested by Prof. H. P. Bowditch that if some substance opaque to the Röntgen rays were swallowed, it could be seen in its passage to the stomach, and the nature of its movement thus determined. Anæsthesia could be dispensed with,--a desirable condition, since observers had found that it interfered greatly with the deglutition reflex. It would be unnecessary to open either the abdominal or the pleural cavity. The reflex stimulus of food, moreover, would be better than electrical stimulation of the superior laryngeal nerve. In short, the animal would swallow normal food under practically normal conditions. At Dr. Bowditch’s suggestion and with his valuable assistance--which we gratefully acknowledge--we made the following series of experiments.

To render the swallowed mass opaque, subnitrate of bismuth was used. The salt is tasteless, practically inert, and can be fed in large quantities without harm. In order that observations could be made by more than one person, all experiments were conducted in a dark room. On the side of the animal opposite the Crookes tube was placed an open fluorescent screen, on which the different tissues of the animal were outlined with varying degrees of light and shade. Among these shadows the swallowed mass appeared as a darker object, and thus its motion could be studied.

For the first experiments the goose was selected. The head and neck were held stationary by a tall pasteboard collar, which allowed free movement of the head without constriction of the neck. The fluorescent screen was placed against this collar at a uniform distance of thirty centimetres from the tube. When a bolus of corn-meal mush mixed with bismuth was placed in the pharynx, it descended slowly and regularly, and occupied about twelve seconds in passing over a distance of fifteen centimetres. The screen was marked at intervals of two centimetres with cross lines, by means of which the relative rate in different parts of the œsophagus could be studied. A vibrator marking tenths of a second was interrupted whenever the bolus crossed a line. An average of over one hundred such observations showed that the rate became slightly slower as the bolus proceeded.

In order to test liquids, molasses was mixed with bismuth to such a consistency as to drop easily from a glass rod. When this was fed with a pipette, it passed slowly and regularly down the œsophagus, clearly by peristalsis. The rate was about the same as for solid food. In both these experiments the addition of water would sometimes cause irregularities in the descent. Microscopic sections from four different parts of the œsophagus of the goose showed no histological difference.

In the experiments on the cat, the animal was placed on its back and left side on a holder. The extremities were secured by straps. The head was held between two upright rods, connected above by a thong; this allowed free movement of the head, without resistance to the passage of food. Shreds of meat dipped in bismuth were ordinarily masticated and swallowed without difficulty. For soft solids, bread and milk were used, so fluid as to be easily drawn up into a pipette. The insolubility of the bismuth salt rendered the study of liquids more difficult. Strong solutions of potassic iodide and other salts, and suspension of bismuth, in acacia and molasses were tried; but a simple mixture of milk and bismuth, shaken in a test tube and immediately drawn up into a pipette, was found most practicable.

Inasmuch as the movement of these different foods varied in different parts of the œsophagus, it will be convenient to divide the latter into three sections. The first or cervical portion extends from the pharynx to the thorax; the second or thoracic, from here to the lower half of the heart; and the third comprises the rest of the canal. The relative length of these three parts is about in the ratio of 9:8:6.

The beginning of deglutition was noted by one observer by a finger on the larynx; the same observer called out when the bolus arrived at the thorax, heart, and stomach respectively, while the other observer noted the time. The movement of solids will first be considered. The descent the entire way was by peristalsis, but the rapidity varied. The duration of the movement in the cervical portion was two and a half seconds, and in the thoracic region a little less than two seconds. At the lower end of the heart there was sometimes a slight pause. In the lower section, from the heart to the stomach, the movement was decidedly different; the rate was always very slow. The distance was less than one-third of the entire canal, yet the time consumed in this part ranged from six to seven seconds, or three-fifths of the entire time of descent. The character of the movement here was also peculiar. Whereas in the upper sections the passage was uniform and regular, with a slight acceleration in the thoracic region, here it was apparently irregular, for the bolus descended about one centimetre with each inspiratory movement of the diaphragm, and remained stationary or descended very slightly during expiration. Thus a series of hitches seemed to carry the bolus to the cardia. A probable explanation of this peculiar movement is that the stomach and lower œsophagus were pulled down with each descent of the diaphragm. This would make the movement appear irregular, although it was really a slow peristalsis. It may be well to remark here that this movement was invariably observed in the cat with every kind of food.

Semi-solids, namely, a mush of bread and milk, descended in the same way as solids; but the rate was slightly faster in the upper œsophagus, for the bolus took about a second less to reach the cardiac level. From here the rate was the same as with solids.

For liquids, one and a half to two seconds sufficed for the descent to the midheart region. Here there often occurred a long pause, from a few seconds to a minute or more. Then the œsophagus apparently contracted above the liquid, which slowly passed on to the stomach, as already described. Sometimes it seemed as if a swallowing movement, evidenced by a rise of the larynx, started the peristaltic wave. Again, several swallows would succeed one another before the liquid passed on. A few times the bismuth and milk seemed strung out along the œsophagus; some more liquid descending would gather this up, and the whole mass, assuming an ovoid form, would move into the stomach.

Thus in the cat the total time for deglutition varies from nine to twelve seconds. The lowest section presents no change ascribable to a difference in consistency, while in the upper sections the rate does slightly increase with the more liquid character of the food.

In experiments on the dog, bismuth enclosed in capsules or wrapped in shreds of meat was fed as the solid. The general phenomena were as follows: With the rise of the larynx there was a quick, propulsive movement of the bolus, which descended rapidly for a few centimetres, sometimes as far as the clavicle. From this point the rapidity was diminished, yet no pause was observed; the bolus simply moved more slowly. This rate was then continued to the stomach without a slackening of speed in the diaphragmatic region, as was observed in the cat. Semi-solids moved in the same way as solids. The total time of descent from larynx to stomach was from four to five seconds.

Liquids gave even a more decided squirt in the beginning of the movement. To render the œsophagus as lax and free as possible, the head of the dog was released from the upright rods and held by the hands after the food was placed in the mouth. Sometimes the liquid descended rather rapidly as far as the heart, at other times no further than the clavicle; then without a pause it passed on slowly and regularly, reaching the stomach in about the same time as solids and semi-solids.

Thus in the dog and cat but little variation was seen in the swallowing of liquids and solids. The liquids pass somewhat faster in the upper œsophagus. But in some animals the difference of rate with foods of varying consistency is much more marked. In the horse, for instance, mere observation shows a decided variation in the rate of movement in the œsophagus. Liquids shoot along the gullet, while solids move clearly by peristalsis. To determine the rate of solids, one hand was placed on the larynx of a horse to note the beginning of swallowing, and the other hand near the shoulders, where the bolus could be easily felt in its passage. The time consumed by the bolus in passing over a certain distance was measured by a stop watch. The rate obtained for solids, such as hay or grain, was from thirty-five to forty centimetres a second.

For semi-solids, a mixture of bran and water was made, thin enough to run easily between the fingers. Each bolus was watched by a separate observer with a separate watch. The average rate obtained was the same as for solids.

Liquids in the horse pass with a rapidity too great to be affected by peristalsis. Another force must be sought. Among the various muscles supposed to be effectual in moving food into the pharynx, the mylohyoids were shown by Meltzer to be essential. The styloglossi were cut by him without much interference with deglutition, but section of the mylohyoid nerves rendered the act impossible. The activity of these muscles in the horse during swallowing is easily perceived by the hand. Their energetic contraction is a sufficient explanation of the rapid passage of water through the œsophagus. The motion here is more than five times as rapid as that of solids and semi-solids.

Meltzer’s experiment to measure the rate of liquids in man by passing a stomach tube containing litmus paper was repeated by us with some modifications. Congo red paper was used, since it is more sensitive than litmus; it also furnishes a means of differentiating between mineral and organic acids, as the discolouration produced on Congo red by mineral acids is removed by ether. It was thus possible to distinguish between the discolouration produced by gastric regurgitation and that produced by the swallowed liquid. For the swallowed liquid, one-half per cent lactic acid was found most satisfactory, as the colour produced by it on Congo red test paper is almost instantly discharged in ether. By this method the paper was found discoloured within half a second after the rise of the larynx, certainly too short a period for a peristaltic wave to carry the liquid to the neighbourhood of the cardia.