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 juice 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 Insects, but here it is placed above the diges- 

 tive stomach (fig. 112, c). The accompanying figure exhibits 



