Part 14

Consequently, in the sham feeding experiment, by the act of eating, the excitation of the nerves of the gastric glands depends upon a psychical factor which has here grown into a physiological one, that is to say, is just as much a matter of course, and appears quite as regularly under given conditions as any other physiological result. Regarded from the purely physiological side, the process may be said to be a complicated reflex act. Its complexity arises from this, that the ultimate object is attained by the joint working of many separate organic functions. The material to be digested--the food--is only found outside the organism in the surrounding world. It is acquired not alone by the exercise of muscular force, but also by the intervention of higher functions, such as judgment, will, desire. Hence the simultaneous excitation of the different sense organs, of sight, of hearing, of smell and taste, is the first and strongest impulse towards the activity of the gastric glands. This especially applies to the two latter senses, since they are only excited when the food has already entered the organism, or at least has arrived very near it. It is by the establishment of this passionate desire for eating that unerring and untiring nature has linked the seeking and finding of food with the commencement of the work of digestion. That this factor, which we have now carefully analysed, stands in closest connection with an every-day phenomenon of human life, namely, appetite, may easily be predicated. This agency, which is so important to life and so full of mystery to science, becomes here at length incorporated into flesh and blood, transformed from a subjective sensation into a concrete factor of the physiological laboratory.

We are therefore justified in saying that the appetite is the first and mightiest exciter of the secretory nerves of the stomach, a factor which embodies in itself a something capable of impelling the empty stomach of the dog in the sham feeding experiment to secrete large quantities of the strongest juice. A good appetite in eating is equivalent from the outset to a vigorous secretion of the strongest juice; where there is no appetite this juice is also absent. To restore appetite to a man means to secure him a large stock of gastric juice wherewith to begin the digestion of the meal.

LECTURE V

PERIOD OF OCCURRENCE AND IMPORTANCE OF THE PSYCHIC OR APPETITE JUICE IN THE SECRETORY WORK OF THE STOMACH--THE INEFFICIENCY OF MECHANICAL STIMULATION OF THE NERVOUS APPARATUS OF THE GASTRIC GLANDS

The psychic secretion is the normal commencement, in the majority of cases, of secretory activity on the part of the gastric glands. If the meal be subdivided and administered at intervals, the psychic juice appears each time--Demonstration of “appetite juice” in a dog with an isolated gastric _cul-de-sac_. The work of the gastric glands if appetite juice be avoided by introducing food through a gastric fistula unperceived by the animal--Digestion of flesh by the stomach with and without sham feeding--Duration of the secretory influence of sham feeding--After the cessation of the psychic effect, how is the secretory work of the stomach maintained?--Experiments to prove the ineffectiveness of mechanical stimulation: excitation of the mucous membrane by means of a glass rod, a feather, a puff of sand, and by rhythmic dilatation of an india-rubber ball--Contact between the food and the stomach-wall may indirectly call the activity of the glands into play by awakening or increasing the desire for food.

GENTLEMEN,--On the last occasion we made ourselves acquainted with the first normal impulse which, in the natural course of events, calls into activity the innervation apparatus of the gastric glands. This impulse is a mental one, and consists in a passionate longing for food, that which in every-day life, and in the practice of the physician, is called “appetite,” and which everybody, both medical and lay, endeavours carefully to promote. We may now venture to say explicitly, APPETITE IS JUICE, a fact which at once displays the pre-eminent importance of the sensation. Medical science endeavours to assist the debilitated stomach by introducing the active constituent of gastric juice--pepsin--from without, or by prescribing other remedies believed to promote its secretion. It is, however, of interest to follow our experimental investigation still farther. What position is to be assigned to the “psychic” or “appetite-juice”[30] in the course of normal gastric digestion? Is any definite _rôle_ to be attributed to it? What course does gastric digestion take when it is absent? Fortunately to all these important questions satisfactory answers are forthcoming by experiment. We have only to regret that these answers come so late.

Let us recall to memory how the secretion of gastric juice proceeded after feeding with flesh or bread in the case of our dog with the isolated miniature stomach. The following are the quantities and digestive capabilities of the first two hourly portions of juice after the administration of 200 grams of flesh or bread (experiments by Dr. Chigin):

═════╤═══════════════════╦═══════════════════ │ Flesh. ║ Bread. Hour.├————————-┬————————-╫—————————┬————————— │Quantity │Digestive║Quantity │Digestive │of juice.│ power. ║of juice.│ power. —————┼————————-┼————————-╫————————-┼————————— 1st │12.4 c.c.│ 5.43 mm.║13.4 c.c.│ 5.37 mm. 2nd │13.5 ” │ 3.63 ” ║ 7.4 ” │ 6.50 ” ————-┴—————————┴————————-╨—————————┴—————————

You see at once that the secretion of the first hour is identical in the two cases both as regards quantity and digestive power, and only in the second is the secretory work differentiated according to the nature of the food. How are we to explain the secretion which takes place at the commencement? Is it not the same which we have already seen in the sham feeding experiments? Is not this first onrush of the stream of secretion the preliminary psychic juice? Unquestionably, gentlemen, this is the case, and we may convince ourselves of the fact in the most diverse ways. Above all, the following is clear: whatever occurs in the so-called sham feeding cannot wholly be absent in the case of normal feeding, since the former is nothing else than the isolated commencement of normal digestion. This justifiable inference is fully confirmed, if the secretion of the first hours after the administration of flesh and bread be compared with that after simple sham feeding. In the case of feeding with flesh and bread, the identically similar and high digestive power of the first hourly portions is striking, and this power coincides with what we have met in sham feeding. Further, if the quantity of juice from the miniature stomach during the first hour be compared with that produced by the non-resected part of the organ,--to do which we must multiply it by ten, since the resected _cul-de-sac_ is approximately one-tenth of the whole organ,--it is here again found that the quantity approximately corresponds to the mean values obtained by sham feeding. Finally, the depression in digestive power or quantity of juice (with flesh, decrease of digestive power; with bread, decline in the quantity of juice), which sets in soon after the taking of food, indicates that the two conditions are connected with the ingestion of food--_i. e._, with a transitory factor which soon passes away and gives place to other conditions. Our explanation becomes still more convincing when we take into consideration the effects of other foods. If you give the dog, for example, something else to eat which does not interest it to the same degree as flesh or bread, you will find the initial increase in quantity and strength of juice does not appear. Offer the animal milk, for example, which in sham feeding, especially if it does not last long, calls forth, as a rule, no secretion, or at all events only very little, and the rapid flow of the commencement--the already-mentioned initial rise--absolutely fails to appear. You have already seen the figures which deal with this matter; I think it necessary, however, to bring them forward again in order that you may be better able to compare them with the secretion after flesh and bread.

The dog was given 600 c.c. of milk (experiment by Dr. Chigin).

Hour. Quantity of juice. Digestive power. 1st 4.2 c.c. 3.57 mm. 2nd 12.4 ” 2.63 ”

We have now begun the analytical examination of the variations of our secretory curve. But owing to the importance of the matter we did not confine ourselves to conclusions which might be drawn from earlier investigations. We turned to new forms of experiment for further proof.

Thus we divided the ordinary ration of flesh given to our dogs--400 grams--into four equal parts, which were administered at intervals of an hour and a half. (Experiments by Privat docent Kotljar and Dr. Lobassoff.) Each time after the dog received its 100 grams of flesh we were able to detect a rise both in the quantity and in the digestive power of the juice. The following table shows the figures in question:

══════════╤═══════════╤═══════════╤═══════════════════════ Half-hour │ Quantity │ Digestive │ periods. │ of juice. │ power. │ Remarks. ——————————┼———————————┼——————————-┼——————————————————————— 1st │ 3.1 c.c. │ 5.13 mm. │ 100 grms. flesh given. 2nd │ 5.0 ” │ 4.63 ” │ 3rd │ 4.7 ” │ 4.50 ” │ 4th │ 5.4 ” │ 4.88 ” │ 100 grms. ” ” 5th │ 5.5 ” │ 3.38 ” │ 6th │ 4.7 ” │ 2.75 ” │ 7th │ 6.0 ” │ 3.75 ” │ 100 grms. ” ” 8th │ 5.4 ” │ 2.50 ” │ 9th │ 5.9 ” │ 2.50 ” │ 10th │ 5.4 ” │ 3.88 ” │ 100 grms. ” ” 11th │ 5.3 ” │ 3.0 ” │ 12th │ 4.2 ” │ 2.5 ” │ ——————————┴———————————┴——————————-┴—————————————————————————

In the curve which follows, only the variations of digestive power are represented.

It is clear that the increase, both of digestive power and of juice volume, is connected with the act of taking in food.

It appeared of interest definitely to determine the volume and properties of the secretion called forth by the act of eating in the dog with the isolated stomach. We endeavoured, therefore, at the beginning, to imitate the conditions of sham feeding as they occurred in the case of the dog with divided œsophagus. In addition to the fistular orifice leading into the isolated miniature stomach, another was opened into the main portion of the organ. If we now fed the dog in the ordinary way with small pieces of flesh, these were received back again at the orifice of the latter fistula, covered with saliva. Precisely as in sham feeding, after five minutes the juice began to flow simultaneously, from both the large and small stomachs. The secretion ran a corresponding course in the two cavities and ceased at the same length of time in both after the administration of food was stopped. Here is an instance taken from such an experiment performed by Dr. Lobassoff.

[Illustration: FIGURE 1.--Curve of digestive power constructed from the foregoing table.]

In five minutes the dog had eaten eighty pieces of flesh (weighing 172 grams), all of which soon afterwards dropped out at the fistula. The secretion began in both stomachs after the lapse of seven minutes from the commencement of the feeding, and proceeded as follows:

══════╤═══════════════════════╦══════════════════════════════════ │ Miniature stomach. ║ Main stomach. ├——————————-┬———————————╫—————————————┬———————————————————— Hour. │ Quantity │ Digestive ║ Quantity of │ Digestive power. │ of juice. │ power. ║ juice. │ ——————┼——————————-┼——————————-╫—————————————┼———————————————————— 1 │ 7.7 c.c. │ ║ 83.2 c.c. │ 5.35 mm. │ │ ║ │} In consequence of │ │ ║ │} a mixture with 2 │ 4.5 ” │} ║ 58.1 ” │ } bile (10-15 c.c.) │ │ }6.25 mm ║ │ } the digestive 2½ │ 0.6 ” │} ║ 8.5 ” │} power was greatly │ │ ║ │} reduced. ——————┴——————————-┴——————————-╨—————————————┴————————————————————

The secretion from both cavities also came to an end at the same time.

This experiment proves to us, first, that the main and miniature stomachs work in perfectly parallel manner with each other. The beginning, the end, and the intermediate variations of the secretion correspond in both cases. Secondly, the digestive power of the secretion coincides in both, and is the same which was observed in the so-called sham feeding. It has here remained at the same height till the cessation of the secretion, without falling to the lower value which we observed from the beginning of the second hour onwards, after normal flesh feeding.

This was also confirmed later, when we performed an œsophagotomy on the dog, and carried out sham feeding in typical form. Here follows one of these experiments taken from Dr. Lobassoff’s article.

The first drop of juice appeared from both cavities during the sixth minute after commencing the feeding, which was kept up for half an hour. The further course of the secretion was as follows:

══════╤══════════════════════════╦══════════════════════════ │ Miniature stomach. ║ Main stomach. ├————————————-┬————————————╫———————————————┬—————————— Hour. │ Quantity │ Digestive ║ Quantity │ Digestive │ of juice. │ power. ║ of juice. │ power. ——————┼————————————─┼————————————╫——————————————─┼—————————— 1st │ 7.6 c.c. │ 5.88 mm. ║ 68.25 c.c. │ 5.5 mm. 2nd │ 4.7 ” │ 5.75 ” ║ 41.5 ” │ 5.5 ” 3rd │ 1.1 ” │ 5.5 ” ║ 14.0 ” │ 5.38 ” │———— │ ———— ║ ————— │ ———— │13.5 (total) │ 5.75 (mean)║123.75 (total) │ 5.5 (mean) ——————┴—————————————┴————————————╨———————————————┴———————————

The secretion came to an end in both stomachs at the same time.

The above is represented in curves in Figs. 2 and 3, the scale on which that for the main stomach is drawn being ten times less than that for the small. As you see, the progress of secretion is identical in both.

The existence of a fistula leading into the large stomach affords us also the possibility of performing an experiment upon our dog which is exactly the converse of the sham feeding experiment, and which constitutes a real _experimentum crucis_. While in sham feeding, we had only, so to speak, the beginning of digestion before us, we are now able in our cross experiment to start at the continuation of this beginning. For this purpose it is only necessary to bring the food into the stomach through the fistula, without attracting the dog’s attention. Since in this experiment it is above all necessary not to excite the dog’s appetite, it is best to carry out the procedure on the sleeping animal. I may add at once, however, that the same result can be obtained on the waking animal, only the process must be performed unnoticed, and the animal’s attention must be diverted from thoughts of food.

[Illustration: FIGURE 2.--Curve of secretion from the miniature stomach.]

[Illustration: FIGURE 3.--The same from the main stomach reduced ten times.]

The results of this experiment are striking, and do not in any way resemble the secretion after normal feeding. Some kinds of food, for instance bread and coagulated white of the hen’s egg, when directly introduced into the stomach, do not yield a single drop of juice during the first hour or more afterwards. This holds good both for the small and large stomachs. When a glass rod is introduced into the food contained in the organ it remains dry. Flesh, if introduced at this stage, is able to excite a secretion, but the appearance of the juice is considerably retarded. It begins from fifteen to forty-five minutes after the feeding, instead of from six to ten, is under normal circumstances extremely scanty during the first hour (3 c.c. to 5 c.c. instead of 12 c.c. to 15 c.c.), and possesses a very low digestive power.

Here is an experiment by Dr. Lobassoff:

400 grms. of flesh were brought into the stomach.

Hour. Quantity of juice. Digestive power. 1st 3.7 c.c. 2.0 mm. 2nd 10.6 ” 1.63 ” 3rd 9.2 ” 1.5 ” 4th 7.0 ” 1.88 ” 5th 5.6 ” 2.25 ” 6th 6.6 ” 2.63 ” 7th 7.5 ” 1.88 ” 8th 5.3 ” 2.0 ” 9th 3.0 ” 5.0 ” 10th 0.2 ” — ”

The secretion began twenty-five minutes after introducing the food. I now ask you to compare the following tables:

┌────—┬——————————————————╥——————————————————╥——————————————————┬———————┐ │ │Fed with 200 grms.║Flesh (150 grms.) ║ Sham feeding │ Total │ │ │of flesh (Chigin).║brought into ║ (Lobassoff). │ quan- │ │ │ ║stomach(Lobassoff)║ │ tity │ │Hour.├————————┬—————————╫————————┬—————————╫————————┬————————-┤ in two│ │ │Quantity│Digestive║Quantity│Digestive║Quantity│Digestive│experi-│ │ │of juice│ power. ║of juice│ power. ║of juice│ power. │ ments.│ │ │ c.c. │ mm. ║ c.c. │ mm. ║ c.c. │ mm. │ │ ├—————┼————————┼————————-╫————————┼—————————╫————————┼————————-┼———————┤ │ 1st │ 12.4 │ 5.43 ║ 5.0 │ 2.5 ║ 7.7 │ 6.4 │ 12.7 │ │ 2nd │ 13.5 │ 3.63 ║ 7.8 │ 2.75 ║ 4.5 │ 5.3 │ 12.3 │ │ 3rd │ 7.5 │ 3.5 ║ 6.4 │ 3.75 ║ 0.6 │ 5.75 │ 7.0 │ │ 4th │ 4.2 │ 3.12 ║ 5.0 │ 3.75 ║ — │ — │ 5.0 │ └—————┴————————┴—————————╨————————┴—————————╨———————-┴—————————┴———————┘

The progress of juice secretion in the above is also represented in the following curves:

[Illustration: FIGURES 4-7.—A. Ordinary curve of gastric secretion (200 grms. flesh). B. Curve from direct introduction of food (150 grms. flesh). C. Sham feeding with same. D. Summation of B and C.]

As you see, the curve which represents the results of the direct introduction of flesh ascends much more slowly and does not attain anything like the height of that caused by normal feeding with the same food. But if the quantities obtained by direct introduction of the flesh be added to those of sham feeding, the resulting curve is almost identical with the normal.

In like manner the digestive power of the secretion in the foregoing experiments can be dealt with, and with the same result. It is a good instance of how a secretion curve can be synthetically constructed from its constituent factors.

Finally, I am able to demonstrate to you the following instructive experiment. In the presence of some of my listeners, whom I had invited to attend an hour before the lecture, I carried out the following procedures on two dogs, both of which had ordinary gastric fistulæ and were, besides, œsophagotomised. Into the stomach of one, while its attention was distracted by patting and speaking kindly to it in order to avoid arousing any thoughts of feeding, a definite number of pieces of flesh were introduced through the fistula. The morsels were threaded on a string, the free end of which was fastened to the fistular cannula by inserting a cork. The dog was then brought into a separate room and left to itself. A like number of pieces was introduced into the stomach of the other dog in the same way, but during the process a vigorous sham feeding was kept up, the animal being afterwards left alone. Each dog received 100 grams of flesh. Since then an hour and a half have elapsed, and now we may draw the pieces of flesh out by means of the thread and weigh them. The loss of weight, and consequently the amount of flesh digested, is very different in the two cases. In that of the dog without sham feeding the loss of weight amounts to merely 6 grams, while the flesh withdrawn from the stomach of the other dog weighs only 70 grams, that is to say, was reduced by 30 grams. This, therefore, represents the digestive value of the passage of food through the mouth, the value of an eager desire for food, the value of an appetite.

I give also a series of figures obtained by Dr. Lobassoff in analogous experiments. Into the dog’s stomach 25 pieces of flesh (100 grams) were brought. The flesh remained two hours in the cavity. Without sham feeding 6.5 per cent, with eight minutes' sham feeding 31.6 per cent, of the quantity was digested.

Again: the flesh remained an hour and a half in the stomach; without sham feeding 5.6 per cent, with five minutes' sham feeding 15 per cent, was digested.

Once more: the flesh remained five hours in the stomach; without sham feeding 58 per cent, with sham feeding 85 per cent, was digested, the balance of undigested food being 42 per cent in the one case and 15 per cent in the other.

I must, however, add that from the nature of this experiment it is not well adapted for class demonstration, and may often fail. On the one hand, it is not at all easy to conceal the introduction of the flesh from the dog; on the other, the unusual and distracting surroundings of the animal often causes a short period of sham feeding to have less effect than would otherwise pertain. In order to avoid such failures it is better before an audience to carry out this experiment only on dogs accustomed to appear in the lecture theatre, and of whose temperament the experimenter is well assured.

I hope you have now been convinced of the great importance which is to be attached to the passage of food through the mouth and œsophagus, or, in other words--and this, according to our former experiences, means the same thing--to the eager desire for food. Without this longing, without the assistance of appetite, many forms of food-stuffs which gain entry to the stomach remain wholly devoid of gastric juice. Others, it is true, excite a secretion, but the juice poured out is scanty and weak.

It is only later, when we have still more fully recognised the conditions upon which the secretory work of the gastric glands depends, that we shall be able to grasp the meaning of these facts in a more comprehensive manner. For instance, why does bread brought unnoticed into the stomach of the dog cause no secretion for hours, while flesh tolerably soon (after twenty to forty minutes) provokes this act? This will be explained in the next lecture; now, however, we must consider other questions.

How long does the after-effect, the echo of the first impulse to the secretory nerves of the stomach, continue to last? How long does appetite juice continue to flow after the normal act of eating, which, especially in the case of animals, is not of long duration? We have already determined many times, not only on our dog with the isolated stomach, but also on other animals, how long the after-effect of sham feeding is continued.

Here, for example, is an experiment from the article of Professor Ssanozki which deals with the point. The dog had a gastric fistula and also an opening leading into the œsophagus. After a sham feeding of five minutes the secretion began, and was continued as follows:

Time in minutes. Quantity. Digestive power. 10 25.5 c.c. 8.1 mm. 10 20.0 ” 8.0 ” 10 13.5 ” 6.8 ” 10 11.0 ” 7.5 ” 10 8.5 ” 8.1 ” 10 6.5 ” 9.0 ” 20 13.5 ” 7.4 ” 20 11.0 ” 7.2 ” 20 7.0 ” 7.2 ” 20 11.5 ” 6.8 ” 20 11.0 ” 6.5 ” 30 6.5 ” 7.6 ” 20 5.5 ” 7.2 ”

The effect, therefore, even after a short period of sham feeding, stretches over a length of time. Naturally the same holds good for the taking of food in the normal way. One must, however, bear in mind that in sham feeding, with all the force and reality of a hunger sensation not satisfied, the eager desire for food, the effective agency, becomes more and more accentuated, and therefore the secretory influence is prolonged and more powerful. In normal feeding, however, the quelling of the longing, the feeling of satisfaction which, as is well known, sets in long before the termination of the digestive period from the mere filling and distension of the stomach, must diminish the desire for food, and, consequently, bring the secretory effect to an end.