the latter of which they closely resemble in function and structure, save that they are spread out under the mucous membrane of the upper part, and the concavity of the gut especially.

The Gland Cells.-Throughout the whole canal are found glands, or rather shut cells, of a shape aptly compared to an India-rubber bottle, with the broader end set in the areolar coat. They appear the size of a mustard seed when viewed by

holding the gut up to a strong light. Some are scattered singly (glandulæ solitariæ), some grouped (glandulæ agminatæ), into about 18 or 20 oval patches, 2 or 3 inches long, chiefly found in the ileum. The latter are usually named after Peyer, who accurately described them; but they were previously mentioned by Grew before the Royal Society of London. Allen Thompson describes in many of them a muscular pupil-like opening, as if they had burst and discharged their contents. They often lie in the angle made by the dividing of a vessel which forms a plexus about them, and sends loops into them-as in the spleen cells represented further on, which they seem to most closely resemble. Such cells may be found also in the liver. They were formerly supposed to produce the intestinal juice, but they are much more probably absorbent organs, in which chyle-cells or molecular base may be elaborated, such being much more abundant in lacteals coming from near the Peyerian patches. They are also said to confer the peculiar odour on the fæces; and

Peyerian Gland half set in submucous tissue, surrounded by two of the follicles which open into the depression at its free end. Villi and follicles are seen around it.

it may be that decomposing matters and animal poisons are eliminated by them.

Schmidt guesses that about 10 ounces of intestinal juice is poured out. We have no information as to its composition, but is supposed to act on starch, which it saccharizes, either if mixed with it, or if confined in a loop of intestine. It acts on fat and albuminoids, as they are certainly assimilated if introduced, as in nutritive enemata. The bowels are constantly undergoing a vermicular action, which can be readily seen by opening the abdomen of a rabbit lately fed. The animal should be rendered insensible by a blow over the medulla oblongata. The contractions proceed downwards, the gut being distended by food below the constriction, and also above as relaxation succeeds. In man, wounds and great emaciation of the parietes have rendered them visible. Electricity much increases these motions, which are ordinarily excited by the contact of food acting on the sympathetic, and perhaps by the distension of the muscular fibres by gas. The intestinal gases vary, as shown by the following table, in various parts of the digestive canal:

This last gas is often eructated in oxaluria. The nervous system seems to influence the secretion of gas. They often distend the intestines in hysteria and fevers (meteorism). In the cœcum, or first portion of the great intestine, an acid juice is poured out, but how far it effect any digestive action, is unknown. After this, the alimentary mass is destitute of any nutritive material,

may

and all future provisions are for its expulsion. As the fæces pass down the great intestine, they become more solid, are moulded to the shape of the gut, and, lastly, remain in the rectum for defecation.

In the lower Bowel the fæces do not bear on the anus constantly, but are supported by 3 valves, described first by Houston. One is found at the beginning of the gut, a second about the middle of it, and a third lies about 3 inches from the anus. They act like "shelves to pack the fæces on," and when the bowel is empty, may be so close as to render the introduction of a bougie difficult.

The external and internal sphincters keep the lower end of the rectum closed till they are overcome by the detrusive efforts of the intestine, assisted by the diaphragm, abdominal muscles, and other muscles which act in expiration. The sphincters are kept closed by tonicity and the absence of any direct antagonistic, rather than by constant muscular action, which should tire. The rectum pours out thick mucus, which lubricates, and so facilitates the expulsion of the fæces. The desire for evacuation of the contents of the gut is usually excited by its distension; but greater bulk, or irritating qualities of the mass, or an over-sensitive state of the mucous membrane, may render the act a reflex one.

Habit has much to do with the frequency of defæcation, as shown by the two instances related by Heberden one individual having a motion habitually but once a-month, and another who had one twelve times daily for thirty years. A distinguished surgeon of this city has informed me of a remarkable instance of the influence of habit over defæcation: a clerk in a public office went to stool on every week-day at a certain hour at his place of business, but was never able to free his bowel on Sunday. A healthy man passes daily about five or six ounces of solid fæces, there being much more on a vegetable than on an animal diet. The

remains of the food which are found in the fæces are in highly oxodized condition, and Liebig has given the characters and odours of fæces to food by fully oxidizing it with liquor potassæ. Their smell, which is not very dissimilar from that of blood and skin, and their colour are mainly derived from the bile. The microscope discovers disintegrated muscular fibres, cartilage cells, elastic tissue, fat cells, spiral vessels of vegetables, mucus, and the ammonio-magnesian phosphate, which salt was once believed to occur only in cases of typhus fever. Only of the bile the liver secretes is discharged by this channel. On analysis, Berzelius found solid excrement to consist of

Water....

Bile......

Albumen..

Peculiar extractive

Salts.

Insoluble residue of food.

animal matter.......

Mucus, fat, bile-resin, and peculiar)

75.3

0.9

0.9

2.7

1.2

7.0

14.0

Much of the matter introduced into the alimentary canal is removed by other channels, as shown by Barral, who performed experiments on himself to determine the daily amount of ingesta and egesta. His results are given in ounces :

QUESTIONS FOR EXAMINATION.

JUNIOR.

1. What divisions of food have been adopted?

2. In what regions are saccharine and fatty foods, respectively, adopted by man?

3. Arrange a list of ordinary foods in the order of their nutritive qualities.

4. State some of the effects of cooking on flesh, and the best methods of extracting soups.

5. Describe the varieties of bread and the relative nutritive value of each.

6. What ideas have been entertained as to the proximate cause of hunger?

7. Enumerate the stages of digestion.

8. Describe the structures which form the crown of a tooth.

9. State the composition and uses of saliva.

10. Enumerate the coats of the stomach and describe the most internal.

11. What uses have been assigned to the pancreatic juice? 12. How are the gland cells of the small intestines arranged, and what ideas are entertained as to their purpose?

SENIOR.

1. Cite the arguments for and against the statement that alcohol is respiratory food.

2. State some of the advantages of retaining the blood in fleshmeat.

3. Adduce some instances showing the need of a mixed dietary. 4. By what physiological principles should the times of meals be regulated for adults and children?

5. State the symptoms, post mortem appearances, and time of death in case of starvation.

6. What proofs can you offer that thirst is not merely a local sensation?

7. Describe mucous membrane and state where each variety of epithelium occurs.

8. Detail Goodsir's observations on the development of teeth. 9. Describe the modes in which solids and fluids are swallowed. 10. From what cases have physiologists obtained most information on the subject of stomachic digestion? detail some of the observations.

11. Describe the structure and functions of the villi.

12. Give the composition of the gaseous and solid alimentary excreta ?