2y 6 Brain of Birds. [Book IX. 



can be obferved here : which parts therefore cannot 

 be confidered as neceflaryto the functions of life j we 

 mighf, however, be led to imagine, that they are fub- 

 iervicnt to the fuperior intellectual powers of the hu- 

 man mind, did we not find that quadrupeds have thefc 

 parts as well as men. Thefe appearances feem rather 

 to depend on the various difpofition and direction of 

 the fibres which compofe the brain j and the particular 

 ufes which have been afiigned to the different parts of 

 the brain feem to have no other foundation than the 

 fancy of authors, who have indulged themfelves in 

 fruitlefs fpec illations. Thofe birds which feek their 

 food below the furface of water, mud, &c. have 

 large nerves which run quire to the extremity of the 

 bill, by which the fenfation of that part is rendered 

 more acute. 



From the medulla oblongata, which is formed by the 

 union of the cerebrum and cerebellum, arife not only 

 the fpinal marrow, but almoft all the other nerves 

 which perforate the bale of the cranium. 



The medulla fpinalis, or fpinal marrow, is a conti- 

 nuation of the medulla oblongata, which paries through 

 the great foramen of the cranium, and is continued 

 lown the bony canal formed by the vertebrse. The 

 figure of the fpinal marrow is comprefied, being flatter 

 behind than before, where we obferve a continuation 

 of thofe grooves which divide the medulla oblongata 

 into its lateral portions. In the medulla fpinalis thefe 

 appear like two cords clofcly applied to each other, 

 but which may be eafily feparated both before and be- 

 hind till we come to their middle, where they are joined 

 together by a thin layer of cineritious fubftance patting 

 from one cord into the other. The fpinal marrow, 

 like the parts of which it is a continuation, confifts of 

 medullary and cineritious fubftance the former, how- 

 ever, 



