THE STOMACH. 51 



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 alternate 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 intervals, 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 exa- 

 mination should be a full-grown young one ; but although, in 

 this almost immature state, the gizzard is fully developed, if 

 we w r ere 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 are able to 

 continue a much longer time without food than others. An 

 Eagle has- been known to fast for three weeks : those who had 

 the charge of it having forgotten to provide its usual supply 

 of food. It soon, however, recovered its strength, and did not 

 appear to suffer from its extraordinary abstinence. How long 

 other birds can sustain hunger, we can have few opportunities 

 of learning, but probably it will be found that such as are 

 most likely, from their habits and particular sort of food, to 

 be more exposed to a precarious and doubtful supply, are, 

 generally speaking, best provided against the chance of suffer- 

 ing. But this is not always the case, for Geese and Fowls 

 which are rarely without the means of supplying themselves, 



