Page images
PDF
EPUB

Fehling's solution to verify the presence of simple sugar. By placing a starch-saliva mixture in the water bath and rapidly making the iodine tests, the student is able to follow the digestive change from starch to erythro-dextrin, to achroo-dextrin and finally to maltose or reducing sugar. The media in which different digestive ferments act are of importance and so in every case the solutions are tested in acid and alkali, in different dilutions and the medium in which digestion best takes place carefully noted.

Gastric digestion is next taken up. The ferments to be used may be obtained from a glycerine extract of gastric juice from a pig's stomach, or a tube may be introduced into a dog's stomach and thus the enzyme taken directly from the living animal. Last year we were successful in operating on a dog and producing a fistula through which we obtained the gastric juice required for work on gastric digestion. Having secured the gastric ferment, text-tubes are provided containing particles of cooked egg albumin, raw meat, cooked meat and any number of the different proteid food stuffs. Each is treated with a liberal amount of the gastric juice. All are placed in the water bath at 40 C. and left there for from one-and-one-half to two hours. The action of the ferment on the appearance of the food is noted from time to time. Chemical tests for the end product of proteid digestion are made from time to time. The Buiret test is used. It is made by the addition of an excess of sodium hydroxide and a drop of copper sulphate, a pink color indicating the presence of peptone, the end product of proteid digestion. In case a solution of commercial pepsin is used, it is necessary to add a two-tenths per cent. solution of hydrochloric acid. As in salivary digestion, both acid and alkaline solutions are used and the surrounding temperature is varied in degree.

In the same manner experiments in pancreatic and intestinal digestion are carried out. To procure the pancreatic secretion the pancreas of the pig or calf is secured and allowed to stand forty-eight hours. It is then ground up with sand in a mortar and a water or glycerine extract is made. This ferment contains steapsin or fat-splitting enzyme, amylopsin or amylolytic enzyme, trypsin, the proteid ferment and a milk-curdling ferment. The part that bile plays in the digestive process is observed by its action on the fats. Last year we were fortunate in securing a specimen of bile from a surgical case in the hospital. The students improved this opportunity to make the chemical tests for human bile.

Experimental work on the normal constituents of urine is taken up with a view of noting the influence which different kinds of diet, amount of liquid taken and exercise have on the amount and on the normal constituents of urine. Each student is provided with a large graduated bottle and required to save the urine for the twenty-four hours. Each day the student is required to make an analysis, determining the total amount of solids, the amount of urea, the specific gravity and the reaction. Tests are made for sugar and albumin, but the work is aimed simply for normal constituents. One day the student will be required to eat exclusively a proteid diet, the next day an excessive amount of exercise is required, the next a carbohydrate diet is taken, and another day large quantities of water are drunk. The weather conditions are recorded each day and a careful record of the analysis of the urine is taken. The results from this method of experimental work are found to give good satisfaction.

This work is followed by work on the blood and circulation. For the chemistry of blood, we provide blood brought from the slaughterhouse, together with blood taken from the dog and also the frog. The specific gravity is taken by Hammerschlag's method, which provides for a medium consisting of a mixture of chloroform and benzol, the former being of very high and the latter very low specific gravity. These two are mixed in a solution of known specific gravity and a drop of blood is suspended, in the mixture. One or the other ingredient is added until the blood is just suspended, then the specific gravity of the mixture is that of the blood. The opacity of the blood is determined by smearing a glass slide with blood and then attempting to read print through it. The so-called “laking" of blood is produced by adding sterile water to blood. This disassociates the hæmoglobin from the corpuscles, as can be shown by repeating the opacity experiment with the laked blood. A normal saline solution does not have this effect on blood. The corpuscles of man as compared with those of the dog and frog are studied under the microscope. A chemical analysis of blood is made. For demonstrating coagulation a dog is provided. Three students are delegated to operate. The anæsthetist first gives the animal a hypodermic injection of 10 c. c. of a one-eighth grain solution of morphia. In a half hour an anaesthetic of alcohol, ether and chloroform is given and the animal is easily controlled. The other two students do the operative work, first introducing a canula into the carotid artery and thus drawing off the blood to be used as desired in making the several experiments. The chemical action that influences coagulation, the temperature, and the fibrin fement that inAuences the clotting of blood may be studied.

The circulation, as far as the action of the heart influences it, can ' be studied. The frog is used for this purpose. The instruments used : are the heart lever and kymograph, with the electric current for stimulation of the vagus. The frog is pithed and the anterior thoracid wall of the animal removed to expose the heart. The apex of heart is. grasped and attached to a delicate lever by silk thread. The drum being prepared for a tracing, a record is made. At each beat of the heart the elements that enter into the heart's cycle may be recorded. After taking a normal tracing as a standard, the action of different stimulii may be tried, such as the effect of extremes of heat and cold, stimulation of the vagi and the effect of drugs like atropia and muscarine. The heart responds very readiiy to these different forms of stimulii and a study of their effects may be made with profit. Having studied the frog's heart, the dog's heart may be studied. The animal is placed under an anaesthetic, the vagus exposed, tracheotomy performed, a tube introduced into the trachea and bellows attached. The thoracic cavity is opened, exposing the lungs and heart. Now artificial respiration is used and the student is able to observe the heart as it beats, to note the change in color as the ventricles contract and the movements of the muscle, and to feel it as it beats. The nervous influence is studied by stimulation of the vagi, and then by cutting them. Respiration is cut off and its action on the heart noted.

A dog also serves our purpose for demonstrating blood pressure and some of the elements that modify it. A dog is anaesthetized and a cannula introduced into the common carotid artery. This cannulais connected with the blood pressure apparatus, which consists of a bottle and rubber tube connected to a mercury monometer provided with a writing lever. The bottle is filled with a solution of magnesium sulphate and elevated high enough to produce sufficient pressure to prevent the outflow of blood from the artery. The writing lever is arranged to make a tracing on the smoked drum. Any rise or fall in blood pressure is noted. The change coincident with respiration is recorded. The effect of stimulation of the vagi, or sympathetic on pressure is noted. The head of the animal is suddenly lowered and then elevated and any changes noted. The effect of ether and chloroform as anesthetics is observed. All of these changes are noted by the monometer's writing lever.

A study of the blood as it circulates in the vessels is made by observations of the circulation in the web of the foot or mesentery of the frog. The frog is pithed and the web stretched over a hole in a thin board. Arranged in this way it may be placed under the microscope and an observation of the blood be made as it circulated. Arteries and veins can be at once distinguished by the character of the flow of the blood. The red and white corpuscles may be studied and the way in which they circulate in the vessels. If the mesentery is used instead of the web after a time from exposure to the air an irritation and consequent inflammation will follow. First there will be an increased supply of blood to the part, then a stagnation of the corpuscles and white corpuscles can be seen oozing through the walls of the vessels.

In the study of respiration there are a few experiments we are able to perform. The factors entering into the act of normal breathing are not easily understood and I have devised an artificial respiratory apparatus to demonstrate them. It is a modification of Hering's apparatus and consists of a 500 c. c. bottle with the bottom replaced by a thin rubber diaphragm. Within the bottle is placed a dog's lungs with the trachea intact. A glass rod is fitted into the trachea and extends through a rubber cork. A monometer is also connected with the bottle. In this way there is provided an intra-pulmonary space within the lungs and an intra-thoracic space between the lungs and the sides of the bottle and the rubber bottom represents the diaphragm. A little air is first pumped from the intra-thoracic space, thus producing a negative pressure, then when the diphragm is pulled down the intra-thoracic pressure is further diminished and the external air fills the lungs. When the diaphragm is allowed to resume its original position the air is forced from the lungs. The monometer registers the changes in intra-thoracic pressure. This apparatus does not provide for the influence of the thoracic walls or ribs on the respiration.

The student is also able to make a respiratory tracing and study the changes which are produced by such influences as temperature and stimulation of the phrenic nerve. A rabbit is used for the experiment. A glass rod is introduced into the trachea of the anæsthetized animal and connected with a rubber tube. This tube is connected with a large bottle, the bottle being connected with a recording tambour. The bottle serves as an air receptacle to furnish the animal with oxygen while the record is being made. The tambour consists of a metal disc covered with a very thin rubber membrane and connected with the tube. A very light lever is arranged in contact with the rubber membrane so that the changes of air pressure in the apparatus caused by the respiratory act are transmitted to the tambour and may be recorded on the smoked drum by the lever. Any variation of breathing affects the lever and is recorded! When the oxygen in the bottle becomes vitiated the breathing becomes exaggerated and a normal tracing can no longer be taken.

It has not been the object of this paper to give a minute, detailed description of the experiments carried out in the laboratory, but to give a general outline of the work. Some of the instruments and methods used have been described more minutely than may seem

necessary to the professional laboratory worker, but the paper is intended to give the general reader an intelligent conception of the work carried out in our laboratory.

[NOTE.-Owing to the limited space which we could place at the disposal of Mr. Burrett, he has not included in his article any reference to the very excellent work being done on the nervous system. This, at our request, he will make the subject of a special article for a future number.— THE EDITOR.]

THE TOMB OF HAHNEMANN.

By Geo. B. Haggart, M. D., Alliance, Ohio. While we are justly proud of our American memorial to the founder of our school of medicine, we cannot but feel that the International Subscription that erected the beautiful monument in the Pere Lachaise in Paris, France, has done a great deal to make the stray visitors to the spot lift up their heads with pride. I recently visited the fine, old cemetery in the east of the city and was much pleased to see the magnificent memorial erected there.

It is built of red granite and is surmounted by a very characteristic bust of the great man whose remains lie below. It is well worthy of the somewhat tiresome journey to go to it.

I imagined that in that great city of the dead, where no doubt thousands sleep and where, as one finds in all European cemeteries, the tombs are almost superimposed, it would be with some difficulty that Hahnemann's grave could be located. However a kindly old Frenchman working on one of the pathways, led us up to the spot without any trouble whatever.

The tomb is much shaded with beautiful shrubs and magnificent trees, so much so that it was with some difficulty that this picture could be obtained.

I was much elated to find that whereas in only a few instances wreaths and flowers had been placed on many tombs, yet our great founder's tomb had been decorated (no doubt by his visiting colleagues and friends) by wreaths, sprays and even some large palm leaves.

The tomb is near the best portion of the famous cemetery. The name of the cemetery arose from that of Pere (Father) Lachaise, the Confessor of Louis XIV. and it is said that he was the only man who in times of the greatest discords in the court, could clarify and bring order out of chaos. I thought as I stood by the tomb of the greatest practical worker in the realm of legitimate medicine since the days of Aesculapius, how well this man, erudite and practical and if need be,

« PreviousContinue »