THE STOMACH. 53 



allows the grain to dribble into the central hole in the 

 upper mill-stone, does it pass onwards to the gizzard, 

 where it is thoroughly bruised and reduced. Many 

 experiments have been made to ascertain the precise 

 manner in which the gizzard acts; but we are still much 

 in the dark respecting it. We may learn, however, a 

 good deal, by examining a very lean young fowl, when, 

 on removing the feathers from the side of the belly 

 nearest the gizzard, its motion can be both felt, seen, 

 and heard. On pressing with the finger, the muscles 

 will feel to the touch as hard as stones; when they 

 relax, the grain, upon which they were then working, 

 passes on, and a further supply, as in the case of the 

 mill, passes under these natural rollers. These alter- 

 nate actions succeed each other slowly but regularly; 

 and on placing the bird close to the ear, as the food and 

 stones roll under the pressure of the muscles of the 

 gizzard, a sound not unlike the noise of the tide rolling 

 upon a shingly shore, may be distinctly heard at inter- 

 vals, as if the waves were ebbing and flowing; and during 

 all this process, the gastric juice slowly flows in from 

 the lower part of the gullet or second stomach, and 

 mingles intimately with the digesting food. 



We have stated that the fowl best calculated for this 

 examination should be a full-grown young one; but 

 although, in this almost immature state, the gizzard is 

 fully developed, if we were to dissect a chick, we 

 should find not a vestige of a gizzard, but merely a thin 

 pellicle or skin. And it is for this reason, that whereas 

 the young fowl is nevertheless old enough to live entirely 

 on grain, and therefore requires the assistance of a 

 gizzard, the little chick, on emerging from its shell, for 

 a short time lives on soft food, and requires no such aid. 

 As it advances in age, however, the pellicle gradually 

 thickens, till at last, by pressure and rubbing, it becomes 

 a hard and grinding membrane. 



From the different construction and digestive powers 

 of the stomachs of birds, it must be evident that some 



