358 ANIMAL PHYSIOLOGY. 
blood, and:the carbonic anhydride found in. the. stomaeh de- 
rived from that fluid. 
It will thus be seen that the alimentary tract has not lost 
its respiratory functions even in man, and that these may in 
certain instances be inordinately developed (reversion). 
SPECIAL CONSIDERATIONS. 
It is a matter well recognized by those of much experience 
in breeding and keeping animals with restricted freedom and 
under other conditions differing widely from the natural ones 
—i. e.. those under which the animals exist in a wild state—that 
the nature of the food must vary from that which the untamed 
ancestors of our domestic animals used. Food may often with 
advantage be cooked for the tame and confined animal. The 
digestive and the assimilative powers have varied with other 
changes in the organism brought about by the new surround- 
ings. So much is this the case, that it is necessary to resort to 
common experience and to more exact experiments to ascertain 
the best methods of feeding animals for fattening, for work, 
or for breeding. Inferences drawn from the feeding habits of ' 
wild animals allied to the tame to be valuable must always, 
before being applied to the latter, be subjected to correction 
by the results of expérience. 
To a still greater degree does this apply to man himself, 
The greater his advances in civilization, the more he departs 
from primitive habits in other respects, the more must he de- 
part in his feeding. With the progressive development of 
man’s cerebrum, the keener struggle for place and power, the 
more his nervous energies are diverted from the lower func- 
tions of digestion and assimilation of food; hence the greater 
need that food shall be more carefully selected, and more 
thoroughly and scientifically prepared. Not only so, but, with 
our increasing refinement, the progress of digestion to suc- 
cessful issues demands that the senses of man be ministered 
to in order that there be no interferences in the central nerv- 
ous system, on the one hand, and every encouragement to the 
latter to furnish the necessary nervous impulses to the digest- 
ive organs and the tissues in every part of the organism: for 
it is not enough that food be digested in the ordinary sense; 
it must also be built up into the tissues, a process depending, 
as we shall endeavor to show later, on the nervous system. 
The “gastronomic art” has, therefore, become of gréat im- 
