PARTS OF ANIMALS, II. xiv.-xv. 



Man has the hairiest head of all the animals. This 

 is (a) due to necessity, because the brain is fluid, and 

 the skull has many sutures ; and a large outgrowth 

 necessarily occurs where there is a large amount of 

 fluid and hot substance. But also (h) it is on purpose 

 to give protection ; that is, the hair affords shelter 

 both from excessive cold and from excessive heat. 

 The human brain is the biggest and the most fluid 

 of all brains ; therefore it needs the greatest amount 

 of protection. A very fluid thing is very liable both 

 to violent heating and violent cooling, while sub- 

 stances of an opposite nature are less hable to such 

 affections. 



This, however, is a digression. We were led into it 

 because the subject was connected with our investi- 

 gation of the cause of eyelashes. Anything further 

 that there is to be said about it will be said in its 

 proper place. 



XV. Both eyebrows and eyelashes exist to afford 

 protection to the eyes : the eyebrows, like the eaves 

 of a house, are to protect the eyes from the fluids 

 that run down from the head ; the eyelashes are hke 

 the palisades which are sometimes put up in front of 

 an enclosure ; their purpose is to keep out things that 

 try to get in." However, the eyebrows are placed 

 Λvhere two bones join (which is why they often get so 

 thick in old age that they have to be cut) ; and the eye- 

 lashes are placed at the ends of small blood-vessels, 

 which have to stop where the skin itself comes to 



the Sight . . . and the like, is well inquired & collected in 

 Metaphisicke, but in Phisicke they are impertinent." But 

 there is no incompatibility, p. 33, " For the cause rendred 

 that the haires about the Eye-liddes are for the safeguard of the 

 sight, doth not impugne the cause rendred, that Pilositie is 

 incident to Orifices of Moisture." See also Xen. 3Iem. i. 4. 6. 



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