receive it, and is then pressed into the pharynx by being

squeezed up against the hard palate; the pharynx is

now dilated by the larynx being moved forward and upwards, save that part behind the nares, which is closed by the palato-pharyngei in the posterior pillars of the soft palate, which is itself thrown up either by muscles or by mere pressure of food. 2. The bolus passes into pharynx, the glottis being closed by the lid-like epiglottis, which is forced down by the pressure of the tongue, the weight of food, and perhaps the arytenoepiglottidean muscles; being very elastic, it springs up as soon as the food has passed; the middle and inferior constrictors now press the bolus into the oesophagus; (3) and is by it forced down into stomach. Professor Corbett, of Queen's College, Cork, has shown that fluids are swallowed in two streams by the sides of epiglottis and the folds which bind it to the arytenoid cartilages, the uvula serving to split the current.

The œsophagus takes a very tortuous course, being in the median line, where it begins about the fifth cervical vertebra, to the left at the seventh, to the right at the third dorsal, below which it crosses the aorta in the posterior mediastinum, and opens into the stomach about one inch below, and to the left of the ziphoid cartilage, and opposite to the tenth dorsal vertebra. The muscular substance of the diaphragm, which it pierces, makes a kind of sphincter for it. The left pneumogastric in front, and the right behind, twine about it, and form the "plexus gulæ." The tube is covered by a lax, distensible areolar coat, and lined by a thick, lowly-organized mucous membrane, which has rather cuticle than epithelium, and a few mucous glands. Some cells of the yeast plant, sarcina, and vibriones, are often found upon it. There are two layers of muscular fibres. The outer longitudinal arises from the vertical ridge on the back of the cricoid cartilage, and is lost on the stomach; the inner, or circular, joins the oblique fibres of the stomach. Both layers are striped muscle above, but they become unstriped about half-way down.

The food does not drop by mere gravity into the

stomach, but is worked down by the successive portions of the tube contracting. Matters are passed against gravity readily through it, as when the horse drinks, in vomiting; and men have exhibited the feat of swallowing while standing on their head. The tortuous course is not enough to prevent the food dropping down, for when the œsophagus is paralyzed or weakened before death, it falls into the stomach with a deep sound, like that of a stone in a well. Electricity produces continued contraction in the upper part, vermicular in the lower. The first stage of deglutition is voluntary, provided there is something to swallow, even saliva; but if this be exhausted we cannot perform the act. It will also occur when volition is suspended, a bolus being often administered to a comatose patient. The second stage is regarded as mixed or automatic; and the third is wholly involuntary. Division of both pneumogastrics causes the food to collect in the œsophagus.

The Stomach of man is a single pouch, narrowed, however, in the middle during digestion-the "hourglass constriction" of Sir E. Home. Its coats are from without inwards (1) peritoneal, continued from diaphragm, liver, and spleen around the vessels; being an indistensible membrane, it is loosely attached by (2) the areolar layer to (3) the longitudinal muscular coat, which is best seen along the curvatures, especially the lesser. 4. Circular fibres are developed at the cardiac orifice where they help the diaphragm in making a sphincter, and at the pylorus where they make a circular valve with an aperture compared to iris and pupil. This valve gradually opens as digestion progresses. 5. Oblique

muscular fibres abound of the great bulging end. Condensed areolar tissue forms a 6th coat, which Sir C. Bell named "nervous" from its colour and plentiful supply of nerves, from the pneumogastrics, left phrenic, and solar plexus. In it also the arteries from the gastric, hepatic, and splenic, and the veins running to the porta,

ramify. The 7th and last plane is the mucous membrane. This surface is thick and velvety, pale and plicated during fasting, extremely vascular and distended during digestion. It is depressed into pits or "alveoli" of an irregularly square form, about in diameter, and of about of the depth of the

membrane. These pits were first ac- Alveoli and Stomachcurately described by Dr. Sprott Boyd,

tubes.

from whose paper the annexed cut is copied. The walls of these alveoli contain abundant capillaries, and from the bottom of them lead

off five or six tubes dip-
ping into the remaining
thickness of the coat.
These stomach-tubes
(sieve-like follicles of Lie-
berkuhn) differ at the car-
dia and the pylorus. At
the cardia they branch
into two or three cœca,
and are lined by round
epithelial gland cells filled
with granules. These are
the true "peptic glands,"
alone secreting acid or
pepsin, according to Köl-
liker. The tubes near the
pylorus do not branch,
are lined by very large
columnar epithelium, and
secrete mucus.
The sto-
mach-tubes of the pig are
here represented. The
motions of the stomach
may be seen when food or

other stimulus is introduced, and the direction of them them is best indicated by a rod inserted through a gastric fistula. The stomach contracts upon the food, which does not escape as the orifices are closed, the contraction being most marked towards the pylorus, or at the centre, producing the hour-glass shape, which can be produced by electric stimulus in animals, or criminals who have been dissected just after execution. This contraction is about four inches from the pylorus, and prevents the food passing through too soon.

That it divides the organ into a cardiac portion for maceration and a pyloric portion for digestion is disproved by the true peptic glands being more numerous towards the cardiac orifice.

The mass of food passes from the cardiac orifice to the bulging end, then along the greater curvature to the pylorus, aud hence back to the cardia along the lesser curvature, the revolution occurring in from one to three minutes. In carnivora the motion is from side to side. That no energetic trituration occurs in the stomach, Spallanzani proved by placing food in perforated metal tubes out of which it was digested. Stimulation of the mucous surface, as by food, renders it red and turgid as a foreign body reddens conjunctiva, and gastric juice oozes plentifully out, none being secreted during fasting. Much slimy mucus is poured out by the stomach, but is at once checked by the section of the vagi, according to Sir B. Brodie. Bernard states that irritation of the pneumogastric nerves promotes, of the sympathetic checks the flow of gastric juice. The Abbe Spallanzani obtained gastric juice by making animals swallow sponges with a string attached for withdrawing it-an experiment I have seen a zealous professional friend perform on himself. Dr. Stevens experimented on a hussar, who had acquired the power of swallowing so many stones that they would rattle on striking the epigastrium; he found that living leeches and earthworms were digested.