80 THE PHILOSOPHY 



the flanksj and avoid the efiefls of his rage by circular 

 movements. He cannot feize any object on the ground 

 with his mouth, becaufe his neck is too fliff to allow his 

 head to reach the earth. He is therefore obliged to lay 

 hold of his food, and even of his drink, with his nofe, and 

 then convey them to his mouth. It is likewife a confe- 

 quence of this frru6Vure, that the young elephants are faid 

 to fuck with their nofe, and afterv/ards pour the milk into 

 their gullet. 



OF THE STRUCTURE OF BIRDS. 

 From the figure and movements of the feathered tribes, 

 we fhould be led to imagine that the ftru6ture of their 

 organs was extremely different from that of quadrupeds. 

 Their oeconomy and manner of living required fome varia- 

 tions in their frame. But thofe variations are by no means 

 fo many or fo great as might be expected. Inftead of hairs, 

 their bodies are covered with feathers, which, belide the 

 beautiful variety of their colours, proted- this clafs of anir 

 mals from the afTaults of rain and cold. They have only a 

 couple of legs ; but Nature has furniflied them with two ad- 

 ditional inftruments of motion, by which they are enabled to 

 rife from the furface of the earth, and to fly with amazing 

 rapidity through the air. The wings are articulated with 

 the breaft-bone, and their motions are performed by mufcles 

 of remarkable ftrength. Many birds are continually pafling 

 through hedges and thickets. To defend their eyes, there- 

 fore, from external injuries, as well as from too much light 

 when flying in oppofition to the rays of the fun, they are 

 furnifhed with a membrane called mcmhrana niclitansy which, 

 like a curtain, can at pleafure be drawn over the whole eye. 

 This covering is neither opaque nor pellucid ; but, being 

 fomewhat tranfparent, it allows as many rays to enter as ren- 

 der any objedl jufl vifible, and enable them to direct their 



