186 TRITURATING ACTION OF GIZZARD-; 
of fluid secreted by its walls, just as it is in the’ paunch of 
ruminant quadrupeds. This crop is of enormous size in some — 
of the granivorous (grain-eating) birds, such as the Turkey. — 
The second stomach (or ventriculus succenturiatus) is the one — 
in which the gastric juicé is secreted; but this is seldom — 
large enough to retain the food, which passes-on through it 
to the gizzard, a hollow muscle, furnished with a hard tendi- 
nous lining. In the granivorous birds this is extremely 
strong and thick ; and pieces of gravel are swallowed by — 
them, which, being worked-up with the food by the action of 
the gizzard, assist in its reduction. In the rapacious flesh-or 
fish-eating birds, however, no such assistance is required, the 
food being easy of solution ; the walls of their gizzard are 
thin, possessing but few tendinous fibres; and the three 
cavities of the stomach are almost united into one. 
201. Various experiments have been made to test the 
mechanical powers of the gizzard of Birds. Balls of glass 
which they were made to swallow with their food, were soon 
ground to powder ; and the points of needles and of lancets, — 
fixed in a ball of lead, were blunted and broken-off by the — 
power of the gizzard, whilst its own internal coat did not 
appear to be in the least injured. On the other hand it has 
been ascertained, that grain enclosed in metal balls which — 
protected it from the mechanical action of the gizzard, but — 
which were perforated so as to afford the gastric fluid free 
access to their contents, was not in the least digested ; so that 
the utility, and even the necessity of this operation, become 
evident. 
202. As there are few animals, save the Mammalia, that — 
perform any proper masticaton in their mouths, the grinding 
down of their food (where it is of such a nature as to require — 
it) must be performed in the stomach ; and accordingly we 
find many tribes, belonging to different divisions of the animal 
kingdom, in which a gizzard, or something analogous to it, — 
exists. It is possessed by almost all Cephalopods, and by 
many of the Gasteropods. In the walls of the stomach of — 
some of these last, there is a considerable amount of mineral — 
matter deposited, intermixed with the hard tendinous fibres 
of which they chiefly consist. A powerful gizzard is also, 
found in many Jnsects, but here it is placed above the diges- — 
tive stomach (fig. 112, c). The accompanying figure exhibits — | 
