There are two factors concerned in gastric digestion: First, the chemical action already considered; and, secondly, a mechanical action due to the movements of the stomach. The gastric movements are essentially identical to the peristaltic movements of the intestines, but modified by the peculiar arrangement of the muscular fibres in the stomach. A sort of churning is produced of the contents of the stomach, the food being carried from the cardiac orifice, along the greater curvature and back along the lesser curvature of the stomach, while subsidiary currents keep up a circulation of food between the centre of the stomach and the mucous membrane. The pyloric orifice is tightly closed by the contraction of the involuntary fibres forming the pyloric sphincter, and thus the escape of food into the duodenum is prevented. As gastric digestion advances, the pyloric sphincter gradually relaxes, and more and more of the products of gastric digestion escape.

The movements of the stomach gradually increase in force as digestion proceeds, and the acidity of the gastric juice increases in an equal proportion. The exact character of the nervous mechanism governing the gastric movements is very doubtful. It is probably some ganglionic apparatus in connection with the sympathetic system. Section of both pneumogastric nerves causes spasmodic closure of the cardiac orifice of the stomach and accumulation of food in the œsophagus.

The chyme resulting from gastric digestion after leaving the stomach enters the small intestine, where it is subjected to other digestive changes. It will be convenient at this point to describe the structure of the small and large intestine, and of the glands appended to them, the liver and pancreas.

The small intestine forms a convoluted canal, commencing at the pylorus, and ending in the large intestine, at the ileo-cocal valve. It is about twenty feet long in the adult, and its convolutions occupy the middle and lower part of the abdomen, surrounded by the large intestine (Fig. 35). It is arbitrarily divided into three parts, the first ten or twelve inches being called the duodenum, in the concavity of which lies the pancreas, the upper two-fifths of the remainder being named the jejunum, and the lower three-fifths the ileum. Like the stomach, the small intestine has four coats, serous or peritoneal, muscular, submucous, and mucous. The serous coat embraces the whole of the small intestine, except a part of the duodenum. The muscular coat consists of unstriped muscular fibres arranged in two sets, an outer longitudinal and an inner circular. The progressive contraction of this coat from above downwards causes the vermicular or peristaltic movements, by means of which the contents of the bowel are forced onwards. The movements of the intestine occur in a wave-like manner, and involve movements of individual parts, and also a frequent change of position of the whole. The submucous coat consists of areolar tissue, and connects the mucous and muscular coats together.

The mucous membrane shows on its inner surface a finely flocculent appearance, due to minute prominences studding its surface, called 'villi.' It is extremely vascular, one of the most vascular membranes in the body. Like the stomach, it is coated throughout with a single layer of columnar epithelium; and in its deepest part, next to the submucous coat, is bounded by a layer of unstriped muscular fibres (muscularis mucosa). Between these parts it consists

chiefly of tubular glands and retiform tissue, containing abundant vessels and lacteals.

Like the stomach, the mucous membrane presents folds, but, unlike that organ, its folds are not obliterated by distension. These folds, called valvula conniventes, reach transversely across the bowel from one-half to two-thirds of its circumference. Their largest amount of projection is about inch. Each consists of a fold of the mucous membrane, with some submucous tissue between the two layers. The valvulæ conniventes commence an inch or two beyond the pylorus, becoming much more numerous in the upper half of the jejunum, when the distance between them is not greater than the breadth of one of the valves. Below this point they gradually diminish in size, disappearing entirely about the middle of the ileum. They serve to supply a greatly increased mucous surface for digestive purposes, and for the absorption of digested food; and prevent the food from being hurried along too quickly.

The villi, already named, occur only in the small intestine, giving its surface a characteristic velvety appearance. They can be best seen by removing a piece of intestine from a rabbit, washing it carefully, and then examining it with a pocket lens under a shallow layer of water. The water serves to float up the villi. Each villus is to of an inch in width, or more. In the upper part of the small intestine they have been estimated to number from 600 to 1000 in a square inch, and in the lower part from 480 to 800 in the same space. Krause calculates their total

number as at least four millions.

Each villus is practically a prolongation upwards of the mucous membrane. Its free surface is covered by columnar epithelium; inside this is a delicate basement membrane, on which the columnar cells rest; the rest of the villus being occupied by retiform tissue, supporting the ultimate branches of a minute artery, a few unstriped muscle fibres, and one or more lacteal vessels. Minute twigs of nerves are probably also present in the villus. The lacteal vessel lies in the middle of the villus, and either ends in a blind dilated extremity, or there may be two lacteals ending in a loop. The epithelioid cells of the lacteal vessel are continuous with the branched cells of the retiform tissue, and these with the flattened cells of the basement membrane; and it is probable that prolongations from the last-named cells extend between the columnar cells towards the mucous surface. It is possible that the emulsified fat is absorbed by means of these processes into the lacteals; but, according to some authorities, the columnar cells absorb the fat in an amoeboid fashion, and then give it up to the lacteal on their opposite side. The muscular tissue in the villus probably serves to retract the villus and drive the contents of the lacteal vessel into a larger lacteal vessel (Fig. 38) in the submucous tissue, where it joins other lacteal vessels, and finally forms the thoracic duct.

Tubular glands (crypts of Lieberkühn) are found throughout the small and large intestine. They are similar to those in the stomach, only they are never divided. They are simple prolongations downwards of the mucous membrane, lined like the general surface with columnar epithelium; they vary in length from to of a line, and have a diameter of about line.

Brunner's glands, named after the anatomist who first described them, are almost entirely confined to the duodenum. They present transitional forms

Their

small salivary glands, or as the pancreas. lower ends are embedded in the submucous coat. Closed follicles occur in two forms in the small intestine. 1st, solitary glands, and 2nd, agminated glands, or glands of Peyer. The structure in the two cases is identical. Each follicle is about the size of millet-seed, and is composed of retiform tissue, in the meshes of which are embedded numerous lymphoid cells, the whole tissue being traversed by fine capillaries. The follicle is situated chiefly in the submucous tissue, but causes a slight bulging upwards of the mucous membrane; and at this part it is studded all over with villi, while around it the orifices of tubular glands are seen (Fig. 38).

Agminated glands are composed of groups of these lymphoid follicles, each group being arranged lengthwise along the intestinal wall, thus forming an oblong figure, from half to two, or even four inches long. The agminated differ from the solitary follicles in having no villi on their surface. There are thirty or more of them in the whole course of the small intestine.

The large intestine extends from the termination of the ileum to the anus. It is divided into the cœcum, colon, and rectum. Its length is about 5 or 6 feet, or one-fifth of the whole length of the intestine. It has a much larger diameter than the small intestine; and in addition to this feature, it can be distinguished from the small intestine by the occurrence of constrictions at varying intervals, causing the bowel to have a sacculated appearance, and by the presence of three longitudinal bands of muscular tissue.

The cæcum is that part of the large intestine situated below the point of junction of the small and large intestine. It is about 2 inches long, and is situated in the lowest part of the abdomen on the right side. Coming off from its inner and back part is a tapering diverticulum about the size of a large quill, and 3 to 6 inches long, called the appendix vermiformis (Fig. 35). Small foreign bodies such as cherry-stones, may

become impacted in this cul-de-sac, and even perforate through its coats, with a fatal result. The ileocæcal valve, preventing return of the intestinal contents from the large into the small intestine, is composed of two segments which project inwards towards the cœcum, formed of prolongations of the mucous and muscular coats of the ileum. The cœcum is the point at which, when constipation occurs, fæces are apt to get impacted. It will be noticed that the course the intestinal contents have to take after leaving the cœcum is upwards along the ascending colon. The long retention of fæces in the cœcum is apt to lead to inflammation of its coats, and occasionally perforation through them. After the coecum, the ascending colon reaches up to the under surface of the liver; it then stretches across the upper part of the abdomen as the transverse colon, and descends on the left side as the descending colon, forming at its lower part a sigmoid (S-like bend), and then becoming the rectum, which is the terminal part of the bowel. The lower part of the rectum is protected by two sphincters, an internal sphincter not under the control of the will, and an external sphincter controllable by the will. Other voluntary muscles attached to the lower end of the alimentary canal, and to the bones at the lower margin of the pelvis, have an important part to play in the extrusion of the fæces.

The large intestine has four coats, similar to those of the stomach and small intestine, but differing in minor respects. The serous coat is absent over the lower part of the rectum. The muscular coat consists, as in the small intestine, of internal, circular, and external longitudinal fibres, but the longitudinal fibres are chiefly collected into three longitudinal bands, except in the rectum, where they spread out over the whole surface of the intestine The submucous coat resembles that of the small intestine. The mucous membrane differs from that of the small intestine in being smooth and destitute of villi. It presents similar tubular glands to those of the small intestine, only longer and more numerous. Its lymphoid follicles are similar to the solitary follicles of the small intestine, but less prominent.

(To be continued.)

GERMAN SCHOOL SINGING.-Mr. J. S. Curwen has published a report on his investigations in elementary schools in Cologne, Munich, Vienna, and Basil, last summer. These towns, in the order in which he happened to visit them, represent an ascending scale of proficiency in singing. The weak point of the whole is that the study of even the elements of musical notation is postponed until the child is ten years of age, and has probably been singing by ear, in the Kinder-Gartens and lower standards, for six or seven years. By this means the habit of trusting to the ear is formed, and even the elder children, who understand the powers of the notes, and hold the music in their hands, prefer to sing by ear. Such a state of things contrasts unfavourably with the Tonic Sol-fa system, by which children of five may, without any strain, be taught to associate sign and sound in an intelligent manner. Mr. Curwen speaks highly of the artistic results obtained. The singing is chiefly done by ear, and the pieces are prepared with much labour, but they are beautifully finished in style. In Switzerland the teaching of notation is well graded, and fair results are obtained.

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In last month's issue of this magazine will be found a syllabus of a course of sixty lessons on this subject, for Standard III. It is assumed that 'Hughes' Science Readers' will be used in conjunction with this course, for the syllabus is arranged mainly upon the contents of that book. I may here state, parenthetically, that I have been asked by letter, this week, whether I 'know for certain that H. M. Inspector will accept this book, seeing that it does not in its present form contain 120 pages of printed matter and sixty lessons.' In answer to this, I reply that one of the largest schools in South London takes Elementary Science as one classsubject and uses this particular book. The examiner questioned from the book; was delighted with it, and with the intelligence shown in the boys' answers; gave 'excellent' for the merit grant; and, furthermore, the School-management Committee of the London School Board have assessed the report as 'excellent.'

I now propose giving the subject-matter, or bare outlines, of the easy conversational lessons in the syllabus to which I have alluded. The reader will observe that many of the titles have already appeared in the plan of lessons for Standard II. This apparent repetition is, however, inevitable. The teacher will, of course, know how to expand the subject, so as to suit the general intelligence of the children in this higher standard.

LESSON I.-'THE THREE KINGDOMS.' Objects exhibited: Pictures of trees and animals. A few stones. A flower growing in a flower-pot, and a tumbler of water.

Animals and vegetables live, feed, and die, i.e., are animate. Minerals, inanimate. Distinguish between animal and vegetable life: (1) As to the nature of their respective foods; (2) As to mode of obtaining that food; (3) Other points of difference.

Vegetable food is inorganic, or earthy; i.e., mineral. Animal food is organic. Animals wander in search of food. Vegetables must have it supplied on the spot. (If the plant in the flower-pot is withering for want of water, i.e., dying of thirst, it is no use placing a tumbler of water by its side; but a thirsty boy can walk to the tumbler, reach out his hand and drink.) Plants are never warmer than the air around them; living animals are.

Note. These distinctions, although open to exception, yet embody sufficient truth for our present purpose.

LESSON 2.-CLASSIFICATION.

Objects exhibited: A chart showing classification of natural objects: this was described in Standard II. lessons; and is given on p. 59 of 'Science Reader for Standard III.'

Classification places like objects in groups. An object in one class is like others in that class, but unlike those in other classes. Carry the classification of words further than in Standard II., but adopt the same method of using slips of paper as described in a former article of the PRACTICAL TEACHER. Give a classification of an object for which the neighbourhood may be specially noted, i.e., different kinds of coal; or of iron ore; or of skins for tanning, etc.

LESSON 3.-THE MINERAL KINGDOM: ROCKS AND METALS.

Objects exhibited: Specimens of stones and of metals. Pictures of a stone quarry, i.e., the slate quarries at Penryn; and of a metalliferous mine, i.e., a Cornish tin-mine.