ORDER ACCIPITRES. 119 



cular vigour is the powerful and quick respiration which we 

 have already noticed. The immense mass of air continually 

 penetrating into the lungs, and all the aerial sacs and canals 

 of the animal, and being decomposed there perpetually, carries 

 the fire of life throughout the system, warms and reanimates 

 all the organs by continual stimulation. The oxygen gas, 

 flowing into the lungs, and combining with the blood in consi- 

 derable quantities, communicates its stimulating qualities to 

 this fluid, increases the action of the heart, and propels the 

 tide of circulation with inconceivable rapidity. So prompt 

 are the pulsations in the arteries of a bird, that it is with the 

 utmost difficulty they can be counted. The heat which arises 

 from this great vascular action is more considerable in the 

 bird than in the quadruped. The heat of this last is no more 

 than 32° of Reaumur, and it is the same in man ; but the 

 birds have 35°, and even more. Thus they are enabled to 

 sustain with ease the rigour of cold in the elevated regions of 

 the atmosphere ; and thus we see even the little wren pass 

 gaily the coldest winters without perishing. If we see spar- 

 rows and some other birds die during this season, it is for want 

 of nutriment. It is, therefore, by no means credible that ani- 

 mals of so much heat, and which have a respiration so strong 

 and continual, should lethargise, or even plunge to the bottom 

 of the waters without being drowned, as is reported of swalloAvs. 



From this great respiration, and the heat which it deve- 

 lopes, two characters are derived which distinguish birds most 

 eminently ; — those are their voice and their amorous propen- 

 sities, between which, as we shall presently see, there is a very 

 close connexion. 



If we consider that, of all the animals of the earth, the birds 

 have the greatest extent of chest, and the largest lungs in pro- 

 portion to their size; that these lungs, attached to the ribs, 

 are not bounded by any diaphragm ; that they have pouches 

 or membranous sacs, even in the abdomen ; and finally, that 

 the air penetrates into all the parts of their body, we shall 



