314 PHYSIOLOGICAL DEVELOPMENT. 



Another case — a very interesting one, somewhat allied to 

 this — is presented by the ruminating animals. Here several 

 dilatations of the alimentary canal precede the true stomach ; 

 and in these, large quantities of unmasticated food are stored, 

 to be afterwards returned to the mouth and masticated at 

 leisure. What conditions have made this specialization 

 advantageous ? and by what process has it been established? 

 To both these questions the facts indicate answers which are 

 not unsatisfactory. Creatures that obtain their 



food very irregularly — now having more than they can 

 consume, and now being for long periods without any — must, 

 in the first place, be apt, when very hungry, to eat to the 

 extreme limits of their capacities ; and must, in the second 

 place, profit by peculiarities which enable them to compensate 

 themselves for long fasts, past and future. A perch which, 

 when its stomach is full of young frogs, goes on filling its 

 oesophagus also ; or a trout which, rising to the fisherman's 

 fly, proves when taken off the hook to be full of worms and 

 insect-larvae up to the very mouth, gains by its ability to take 

 in such unusual supplies of food when it meets w T ith them — 

 obviously thrives better than it would do could it never eat 

 more than a stomachful. That this ability to feed greatly in 

 excess of immediate requirement, is one that varies in indi- 

 viduals of the same race, we see in the marked contrast 

 between our own powers in this respect, and the powers of 

 uncivilized men ; whose fasting and gorging are to us so 

 astonishing. Carrying with us these considerations, we shall 

 not be surprised at finding dilatations of the oesophagus in 

 vultures and eagles, which get their prey at long intervals 

 in large masses ; and we may naturally look for them too in 

 birds like pigeons, which, coming in flocks upon occasional 

 supplies of grain, individually profit by devouring the 

 greatest quantity in a given time. Now where the trituration 

 of the food is, as in these cases, carried on in a lower part of 

 the alimentary canal, nothing farther is required than the 

 storing-chamber ; but for a mammal, having its grinding 



