applies an expanded termination to a much smaller orifice at the side of the cæcum: the part so included forming the valve. The length of the cæcum is thirteen inches: its widest circumference six inches its parietes are puckered up by two longitudinal muscular bands, one of which is continued a short way upon the colon. The cæcum is marked off from the colon by a valvular structure similar to that at the end of the ileum; the two orifices of the blind gut being analogous to the cardia and pylorus of the stomach.'

In the Coypu the duodenum commences with so large a dilatation that it projects toward the oesophagus like a cæcum; its circumference here was 4 inches; the decrease is gradual, and where the biliary duct enters the circumference is three inches, and a little distance below this 2. The length of the small intestines is sixteen feet, their mean circumference 13 inches. The cæcum is large, making a circular turn at its base and gradually diminishing in volume: it is puckered into sacculi by two muscular bands, less defined toward the basal part: its length is one foot ten inches, its greatest circumference eight inches. The ileum terminates in a sort of sacculus at the base of the cæcum, close to the colon. This gut begins large, but gradually becomes narrow: it is slightly sacculated for a short distance: its mean circumference 2 inches. The colon makes an abrupt turn from the cæcum, and after a course of one foot five inches suddenly folds upon itself, the reflected length running down for the distance of eleven inches, when it turns as suddenly back again, but does not adhere so closely to the previous fold as that to the first length; it then contracts and soon proceeds to constitute the rectum. Near the end of the first loose fold, as in Capromys, the fæces begin to assume a solid form in separate oval masses. The total length of the large intestines was four feet four inches. The enormous cæcum of the Capybara occupies almost the posterior half of the abdomen.

The parallel course of the arteries along the coats of the colon in Hystricida, Chinchillida, and Ctenomyidæ, connected at distant intervals by transverse branches, without other ramification, is worthy of remark.2 In the Porcupine the cæcal sacculi are puckered upon three longitudinal bands, two of which are continued some way along the colon. In the Chinchilla the sacculi project alternately from opposite sides of the cæcum. The abovedefined general form of large intestines in vegetarian rodents is exemplified in fig. 321, from the Water-vole. Here the ileum 'cxxx". p. 70, et seq. for further details of the alimentary canal of this rare rodent. 2 xx. vol. i. p. 215, No. 723, c. cxxx". p. 22, pl. 1.

terminates at the base of the sacculate cæcum, n; the slender termination, q, simulates a vermiform appendage: the colon begins by a pair of large sacculi, r, but quickly contracts to the calibre

shown at s. Two oval

patches are here, as usual, situated on either side of the ileo-cæcal valve. In the Leporide they are lodged in a special pouch, fig. 322, f: the vascular mucous membrane of the cæcum, in these herbivorous rodents, is augmented by being produced into a broad fold, disposed spirally to near the slender termination of the cæcum, d, b, which is glandular, like the vermiform ap

pendage in Man. Three longitudinal bands extend upon the colon; but two of these become blended together as that gut con

tracts, and the sacculi project from one side only, in which the fæcal contents begin to be moulded into the pellet-shaped excrement. After the colon has completed its first long fold, returning to near its commencement, the sacculi disappear.

Besides the analogy already noted between the orifices of the cæcum and those of the stomach, that of the different diameters of the entering and out-going tubes may be observed. Comparative anatomy concurs with results of undesigned experiments, as in ses where artificial openings have been established in the

human intestinal canal, in showing that a change to gastric digestion is repeated upon the food in the cæcum: chemistry has, also, shown that the chyme here again becomes acidified, after having been neutralised by bile in the small intestines.

1

323

h

§ 327. Alimentary canal of Insectivora.-In this, as in preceding orders, the oesophagus is usually prolonged some way into the abdomen before its termination. My examinations of the stomach in the different insectivorous genera lead me to generalise an approximate, rather than a remote, relative position of the cardiac and pyloric orifices: the form of this viscus, in most, accords with that in Ornithorhynchus, fig. 308, b. In a Proboscis-shrew, e. g. (Rhynchocyon, Peters), the depth, or diameter of the stomach in the axis of the abdomen, exceeds the length, or transverse diameter: the cardiac end does not bulge out to the left of the gullet so much as in Rodentia; but there is usually an expansion beyond and to the right of the pylorus, and the proximity of that orifice to the cardia leaves but a short tract answering to the lesser curvature' of the stomach, fig. 323, s. The form of this viscus in Solenodon, Amphisorex, Hydrosorex fodiens, and Cladobates, is very similar to that in Rhynchocyon: in all Insectivora the duodenum expands to much more than the diameter of the oesophagus. In our small native Shrews the shape of the stomach depends much upon the quantity it happens to hold, and the transverse extent prevails most in the empty state. In Sorex araneus the cardiac sac projects moderately beyond the œsophagus; in S. leucodon, Hydrosorex hermanni and Amphisorex tetragonurus, the cardiac sac assumes almost rodent proportions: in many Shrews the contracted pyloric part of the stomach is much prolonged.

In the Hedgehog the transverse length of the stomach prevails over the depth: the blind end to the left is less produced than in the above-named Shrews: the coats of the narrow pyloric end are thick.2

Il est généralement disposé en travers, plus ou moins alongé dans ce sens, avec les orifices distants.' XII. tome iv. p. 34. See also LXII". p. 1002.

2 Hunter notes that he found in the stomachs of Hedgehogs, in April, grubs, with a little unchewed grass; in May, June, July, and August, the insects of the season,' and caterpillars of the cabbage (Pieris Brassica); in September and October,

In the Mole the abdominal œsophagus is long and enters the stomach midway between the two ends: the cavity, when distended with the worms and grubs devoured by this voracious burrower, 'fills nearly half of the abdomen.' In the Tenrecs (Centetes) the cardia and pylorus are further apart than in most Insectivora: the cardiac sac is less prominent; the pyloric end is bent upon itself.

As a rule the intestinal canal is uniform in diameter, and devoid of cæcum in the present order: it is loosely suspended on one continued peritoneal fold from the beginning of the duodenum to the rectum. In the common Shrews, fig. 359, the intestine is about four times the length of the body; in the Hedgehog about six

324

Cæcum and colon, Proboscidian Shrew.

LXXXIV'.

times, in the Mole seven times, that length. The Tupaias and some of the snouted-shrews are exceptions: in the former (Cladobates) the cæcum is simple, straight, about an inch in length, not wider than the major part of the colon; and but little wider than the ileum. Macroscelides has a long, slender, pedunculate cæcum. In Rhynchocyon, the cæcum, fig. 324, c, is about 3 inches long, and is twice the width of the ileum, ib. i. The colon, of similar diameter with the cæcum, forms a short double bend, r, r, returning upon itself, before it is continued on into the narrow portion ending in the rectum.

The lining membrane of the Mole's intestine is disposed, along part of the canal, in close-set longitudinal folds; but is remarkable for its smoothness and absence of visible villi. The mucous membrane of the Hedgehog's intestine is beset with minute flat, conical villi, changing toward the end of the canal into a fine reticulate surface.

§ 328. Alimentary canal of Cheiroptera.-The Cheiroptera present three forms of stomach; one relating to vegetable diet, another to the times of taking the food and to the quantity taken, a third to the ordinary capture of insects during flight. The latter relation, which prevails in the order, is associated with a form of

elytræ, wings and legs of insects, including those of the Scarabaeus and of Geotrupes stercorarius; from November onward to March-the hybernating season-there was no food in the stomach, only a little creamy mucus. ccxxxvI. vol. ii. p. 193. 1 Ib. p. 187.

325

stomach inverted of

common Bat (Ves

stomach, resembling that in the common Shrew. In fig. 325, the cavity has been inverted, showing the ruge and the glandular character of the gastric membrane at the pyloric end. The difference in the diameters of the oesophagus and duodenum are also shown. In the Noctule a small part of the right end of the stomach projects beyond the pylorus. In Plecotus communis the left end of the stomach becomes somewhat attenuated and bent up. In the Vampires (Desmodus) the cardiac portion is produced into a long intestiniform reservoir, in which the blood is stored up, that may have been sucked during a night's adventure, and transported for digestion in the place of repose. In the Pteropines the left end of the stomach, fig. 326, is much produced, but in a far less degree, than in Desmodus. It is sometimes found, in the partially distended state, divided into two dilatations: the extreme one smooth; the other, nearer the cardia, showing rugæ longitudinally disposed: the oesophagus in these frugivorous Bats is wide and expands near its termination. To the right of this

pertilio murinus).

expansion the stomach is long and narrow, bent upon itself, and produced into a cæcal pouch beyond the pylorus, which is extremely small. The intestinal canal is usually devoid of cæcum; but the colon begins

with one about a quarter of an inch in length, in Rhinopoma Hardwickii and Megaderma spasma. The whole intestine is barely thrice the length of the body in Vespertilio murinus: in a Pteropus it is

326

nearly seven times that length. The intestinal villi in some Bats are close-set foliaceous processes, and form extremely beautiful microscopic objects when injected. In Rhinolophus the lining membrane presents fine transverse folds.

The low position of the volant and terrestrial Insectivora, as of Rodents and Marsupials in the Mammalian series, is shown by the loose and simple mode of suspension of the intestinal canal.

§ 329. Alimentary canal of Quadrumana.- The Galeopitheci indicate their lemurine affinities by their long and large cæcum. The œsophagus opens on the cardiac side of the middle of the

A good figure of this modification, first observed by Peters, will be found in CXXXVI". p. 388.