INTRODUCTION. 3 



quickly bring on suffocation. Tiie superior vital heat of this class 

 of beings is likewise probably due to this greater aeration of the 

 vital fluid. 



Birds, as well as quadrupeds, may be generally distinguished 

 into two great classes from the food on which they are destined 

 to subsist ; and may, consequently, be termed carnivorous and 

 granivorous. Some also hold a middle nature, or partake of both. 

 The granivorous and herbivorous birds are provided with larger 

 and longer intestines than those of the carnivorous kinds. Their 

 food, consisting chiefly of grain of various sorts, is conveyed whole 

 into the craw or first stomach, where it is softenjpjd' aj^d acted upon 

 by a peculiar glandular secretion thrown out upon its surface ; 

 it is then again conveyed into a second preparatory digestive 

 organ ; and finally transmitted into the true stomach or gizzard, 

 formed of two strong muscles, connected externally with a tendinous 

 substance, and lined internally with a thick membrane of great 

 power and strength ; and in this place the unmasticated food is at 

 length completely triturated, and prepared for the operation of the 

 gastric juice. The extraordinary powers of the gizzard in commi- 

 nutinor food, to prepare it for digestion, almost exceeds the bounds 

 of credibility. Turkeys and common fowls have been made to 

 swallow sharp angular fragments of glass, metallic tubes, and balls 

 armed with needles, and even lancets, which Avere found broken 

 and compressed without any apparent pain to the subjects, or 

 wounds in the stomach. The gravel pebbles swallowed by this class 

 of birds with so much avidity, thus appear useful in bruising and 

 comminuting the grain they feed on, and preparing it for the solvent 

 action of the digestive organs. 



Those birds which live chiefly on grain and vegetable substances, 

 partake in a degree of the nature and disposition of herbivorous quad- 

 rupeds. In both, the food and the provision for its digestion, are very 

 similar. Alike distinguished for sedentary habits and gentleness 

 of manners, their lives are harmlessly and usefully passed in col- 

 lecting seeds and fruits, and ridding the earth of noxious and 

 destructive insects ; they live wholly on the defensive with all the 

 feathered race, and are content to rear and defend their offspring 

 from the attacks of their enemies. It is from this tractable and 

 gentle race, as well as from the amphibious or aquatic tribes, that 

 man has long succeeded in obtaining useful and domestic species, 

 which, from their prolificacy and hardihood, afford a vast supply of 

 wholesome and nutritious food. Of these, the Hen, originally from 



