r 



172 Notes, ii. 9 — 10. . 



part in time is regenerated. It was believed until very recently that in this case the 

 restoration though externally complete did not extend to the lost vertebrse. . But Legros- 

 {Gaz. Midic. 1869, p. 75) has shown that even these bones are replaced after several 

 years' interval. More rapid restoration of bone had moreover already been observed by 

 Spallanzani to occur after the rem6val of the limbs of water-newts, and great was the 

 astonishment of physiologists when he announced this fact. 



• 12. It will be noted that A. only likens nails, horns, hoofs, etc., to bone in their 

 tactile properties. In other passages {D. G. ii. 6, 50 ; H. A. iii. 9, 2) he says that the 

 former are all developed from the skin, and follow its changes of colour ; and he 

 distinguishes the group of dermal parts thus formed from the bones and the teeth ; 

 which latter he imagines are not dermal but osseous, because they remain white when the 

 skin is black. 



13. Aft organ or heterogeneous part made from a single tissue .or homogeneous part 

 (to eVx»7/iaTf(r|U6ca) wrll have the same name as the tissue. Hoof, nail, cartilage is the 

 name of both organ and tissue. These might therefore be dealt with either among the 

 tissues, or among the organs. The latter plan, says A., is the better ; for it is only by 

 studying the purposes subserved " by the organ hoof or nail, that we can learn fhe nature 

 of the tissue hoof or nail, Cf. ii. I, Note 16. 



(Ch. 10.) . 1. The discussion of the homogeneous parts, or tissues, is now finished, and 

 A. proceeds to consider the heterogeneous parts or organs. 



■ 2, Strangely enough, A. after all does not follow the order here indicated, but begins 

 vvith the brain and other parts of the head, and then proceeds to the neck, thorax, and 

 abdomen, in succession ; following the simple plan of beginning at the top and goirig 

 downwards. 



3. This limitation is introduced because some of the lower animals are without digestive 

 cavities at all (ii. 3, Note 9), and others {H. A. i. 2, 2) without excremental orifice. 

 By the latter A. probably meg-ns Acalephre, which have, he says (Z>. P. iv. 5, 49), no 

 visible excretion; though it must be admitted that elsewhere {H. Ai viii. 2, 15) he 

 speaks of them as having an excremental orifice. 



4. Cf. ii. 3, Note 8. 



5. A similar recognition of the truth, that simplicity of life and simplicity of structure 

 go hand in hand, will be found at iv. 7, i. 



6. Cf. ii. 2, Note 5, and iv. 10, 8. ' • 



7. That man alone is erect is repeatedly mentioned by A. as a proof of his superiority 

 to other animals. Doubtless the erect position, leaving as it does tjie upper extremities 

 free for skilful manual operations, is an important element in man's structure. But 

 this position is not the exclusive privilege of man ; some birds, as the penguin, and some 

 mammals, as the kangaroo, having a vertical attitude. 



8. e.g. Plato in the Timaeus {Jowetfs Trans, ii. 568), who probably borrowed the 

 opinion, as Galen says he did his physiology generally, from Hippocrates. Democritus 

 also had taught that the sovereign part of the squI was in .the head ; and Diogenes of 

 ApoUonia, mofe directly, had held that the brain was the seat of sensation, being 

 surrounded by a layer of hot dry air, which was in connection with the sense-organs by 

 means of the blood-vessels, and so sympathised with their motions and affections (cf. 

 Grate's Plato, i. 65). 



9. Hpw came A. to reject this view of the brain's office in favour of his own apparently 

 less plausible one ? The reasons seem to be as follows : 



a. Firstly, as he says here, and repeats oftentimes (ii. 7, Note 5 ; //. A. iii. 19, 2), 

 the brain is insensible to external mechanical stimulation. If the brain of a living 



\ 



