R. I.J THE HTSTOHY OF ANIMALS. 19 



2. First of all, the brain is placed in the fore-part of the 

 head, and it occupies the same position in all animals that 

 have this part, which belongs to all sanguineous and cepha- 

 lopodous animals. In proportion to his size, man has the 

 Jargest brain of all animals, and the moistest. Two mem- 

 branes enclose the brain : that outside the skull is the strong- 

 est ; the inner membrane is slighter than the outer one. In, 

 all animals the brain is in two portions. The cerebellum is 

 placed upon the brain at its lowest extremity. It is different 

 from the brain both to the touch and in appearance. 



3. The back of the head is empty and hollow in all ani- 

 mals in proportion to their size, for some have a large head, 

 but the part lying under the face is less in those animals 

 which have round faces ; others have a small head and large 

 jaws, as the whole tribe of Lophuri. In all animals the brain 

 is without blood, nor does it contain any veins, and it is 

 naturally cold to the touch. The greater number of animals 

 have a small cavity in the centre of the brain. And round 

 this a membrane filled with veins : this membrane is like 

 skin, and encloses the brain. Above the brain is the smooth- 

 est and weakest bone in the head it is called sinciput. 



4. Three passages lead from' the eye to the brain ; the 

 largest and the middle-sized to the cerebellum, the least to 

 the brain itself. The least is that which is nearest the nostril ; 

 the greater are parallel, and do not meet ; but the middle- 

 sized passages meet : this is most evident in fishes, and 

 these passages are nearer to the brain than the larger, but 

 the least separate from each other, and do not meet. 



5. Within the neck is the oesophagus, which also de- 

 rives its additional name, the isthmus, from its length and 

 narrowness, and the trachea. The trachea lies in front of 

 the oesophagus in all animals which possess this part, that is, 

 all animals which breathe from the lungs. The trachea is 

 cartilaginous in its nature, and contains but little blood : it 

 is surrounded with many smooth rings of cartilage, and it 

 lies upon the upper part towards the mouth, opposite the pas- 

 sage from the nostril to the mouth, wherefore, also, if any 

 liquid is drawn into it in drinking, it passes out of the mouth 

 through the nostrils. 



6. Between the passages is the epiglottis, which can be 

 folded over the passage which extends from the trachea to the 



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