Notes, ii. 6 — 7. 165' 



which the bony tissue is more or less penetrated by an oily fluid ( Todd's Cyclop, iii, 958). 

 The same is true of the bones of Cetacea and of seals {Cuvier, Anat. Comp-. i. 1 10). 

 • 9. Cf..iii. 4, Nqte 20. 



(Ch. 7.) I. As Plato in the Timaeus {JoweWs Transl. ii. 567). 



2. Cf. ii. 5, Note 2. 



3. "In its proper substance" as opposed to the vascular membranes that surround it. 

 As to the supposed bloodlessness and coldness of the brain, cf. ii. 10, Note 18. 



■ 4. A. uses the term fluid with much latitude. Jhus he calls the faeces fluid. This 

 however might be defended,, as they sometimes are so, especially in bovine animals. 

 Here he calls the brain fluid, and Galen also calls it " almost fluid." It is true A. says 

 it is the most consistent of all the animal fluids, and also (Z>. G. ii. 6, 35) that it is only 

 actually fluid in the very young, and afterwards gradually becomes more consolidated. 

 But even with' these limitations the term gives an exaggerated idea of the softness of 

 the part. -Probably A. thought the brain was more fluid during life than after death, • 

 reckoning it, with fat and marrow, among the substances which are fluid only so long as 

 they are in the living body (ii. 2, Note ij. It may be objected to this that A. had at 

 any rate seen the brain of the chamaeleon during the animal's life {H. A. ii. 7), and that 

 he must have known that this was not fluid but solid. But it must be remembered that 

 according to A. 's views the colder the nature of an animal the less fluid should its 

 brain be ; for in his opinion it is on the fluidity of the brain that its coldness depends, 

 and this must be proportioned to the animal's heat, which it has to temper. But 

 the chanigeleon is cold-blooded ; so that the firmness of its brain would be only what 

 A. would expect, and would in no wise lead him to look for like firmness in the brain of 

 a warm-blooded animal. 



It will be noticed that the human brain is said to be more fluid than that of any other 

 aninial. This is not the case. Doubtless A. had never seen an adult human brain. 

 But I think it not unlikely (i. 5, Note l) that he may have examined the brain of an 

 aborted foetus, in which case he would most probably have found the brain diffluent, 

 aind that his statement was founded on this. 



5. This fact may have been learnt from Hippocrates, or some other surgeon who had 

 exposed the brain in an operation, and noticed its apparent insensibility to mechanical 

 irritation. Or it may have been noticed by A. himself in his vivisection of the chamseleon 

 i^H. A. ii. 11). Very possibly it may have been an observation made on that same 

 occasion that led him to the hasty generalization that the brain was always cold. 



6. I take the meaning to be as follows : "The excrements have of course no anatomical 

 connection "wjth the body, but are isolated substances. The brain, though not an 

 excremental substance, yet so far resembles one that it also is without anatomical con- 



. nection with the rest of the body, excepting as already stated with the spinal marrow. 

 In this it differs from the other organs, none of which is ever isolated. Thus (ii. 9, l) 

 every bone is connected with others so as to fonn an osseous system, and similarly 

 every blood-vessel is connected with the rest so as to form a vascular" system. But 

 the brain is isolated. For it is not true as some say that it is anatomically con- 



• nected with the organs of sense, so as to form with them a sensory system." As to 

 the continuity of brain with sense-organs, cf. ii. 10, Note 9. 



7. Democritus {D. A. i, 2). 



8. And therefore causing it to be cold ; for both earth and water are copipounds of 

 cold matter, the former with solid, the latter with fluid matter (cf. ii. i, Note 3). 



9. Elsewhere {H. A. i. 16, -2), A. speaks of Cephalopods in general, and not only 

 of the poulp, as having a brain. The cephalic ganglia in these animals are so large 



