THE ANATOMY OF BIRDS. — SPLANCHNOLOGY. 
213 
zard, gigerium, or muscular division of the stomach, sometimes called the ventriculus hulhoms. 
The two are sometimes separated by a tract, sometimes immediately consequent. In the mus- 
cular gizzard, the food-grist is ground fine. To this end, the walls of "he cavity become devel- 
oped into a more or less powerful muscular apparatus, and the mucous membrane changes to a 
tough, thick, horny, occasionally even bony, lining ; this callous cuticular lining being often 
very loosely attached, and even deciduous in some cases. The muscular arrangement is chiefly 
in two great masses, called the lateral muscles^ converging to a central tendon ; betM^'een them 
intermediate fibres may form a more or less distinct muscular belly. In the most powerful 
gizzards, the muscular tissue is very dense and dark-colored; the tendons brilliantly glistening, 
and the contained millstones" extremely callous. Such a gizzard is well displayed by the 
common fowl or the goose. The opposite extreme is afibrded by the carnivorous and espe- 
cially the piscivorous birds, whose soft food requires little trituration, — it is all a matter of 
degree. How readily this part of the canal responds to the regimen of the bird, is witnessed in 
our cock-of-the-plains {Centrocercus urophasianus) , — a bird whose gizzard is so slightly mus- 
cular as to appear like a membranous bag, though its gallinaceous relatives have extremely 
strong grinders. Its food is chiefly the buds and leaves of the wild sage (Artemisia), and grass- 
hoppers. Increased muscularity of the gizzard has even been artificially produced. Birds 
whose grist is heavy habitually swallow gravel, that these small stones may mechanically aid 
in the grinding process. The action is so energetic, that in auscultating" a fowl when the 
mill is in full blast, the noise of the grinding can be distinctly heard. The pebbles, in fact, 
have a function which leaves ''hens' teeth" not entirely mythical. The kind of motion 
impressed upon the opposing pads of cuticle is alternating, — a rubbing back and forth to a 
slight extent. Peculiar dispositions of the callous surfaces are found in some pigeons, with 
corresponding peculiarity of the cross-section of the gizzard. In some of the cuckoos a matting 
of impacted hairs of lepidopterous insects has been mistaken for a coat of the gizzard itself. In 
the darter, which has a pyloric division or compartment of the gizzard, this is nearly filled with 
a mass of matted hairs, a peculiar modification of the epithelial lining, serving to guard the 
pyloric orifice. Folds of the lining membrane form a pyloric valve in many birds. The pylo- 
rus, or the pyloric orifice, is that opening by which food leaves the gizzard for the intestines ; 
the orifice of entrance from the oesophagus is the cardiac. The two are always near together, 
and sometimes adjoining. (In fig. 101, i, 1c is on the central tendon of the moderately muscular 
gizzard ; the cardiac orifice is between and k, and pylorus between I and k.) 
The Intestine continues the alimentary canal to the cloaca. Any difierence in the 
length of the whole tract, relatively to that of the bird, is chiefly produced by the foldings of 
the intestine, especially in the upper portion of its course. The extremes of proportionate 
length are perhaps not ascertained; but known to be from less than 2:1, to more than 8:1. 
In birds there is little or no distinction between "small" and "large" intestine, as to the calibre 
of the tube, nor is the latter succulated as in mammals. The former is considered to extend 
from the pylorus to the cceca (structures to be presently noticed). Above the caeca the intes- 
tine commonly receives its foldings and windings ; below them it usually proceeds more 
directly, or quite straight, to the cloaca, forming literally a "rectum" ; but in the ostrich this 
ultra-caecal tract is longer than the rest, and convoluted. The cis-csecal portion is convention- 
ally divided into duodenum, jejunum, and ileum ; there is, however, no positive anatomical 
distinction of these parts in any animal with which I am acquainted. In birds, a " duodenum " 
is perhaps as distinct as ever ; it forms the most constant duplication of the intestine, the pan- 
creas being lodged in this duodenal fold (fig. 101, i, I, m, n). The course of the intestine is 
otherwise very various in diS'erent birds. The upper end, near the pylorus, receives the hepatic 
ducts ; and food is chylified after impregnation with the biliary and pancreatic fluids ; a process 
furthered by the proper secretions of the intestinal follicles. The chyle is drawn off by the 
