62 APPENDIX. 



of this attraction ; and, so that this is performed, it matters but little whether or no 

 these vessels accomplish it by means of subordinate nutritive capillaries destined to the 

 circulation or deposition of the nutritious molecules, or by means of organic pores, 

 with which the parietes may be provided. 



But, whilst we suppose that the function of nutrition may thus take place in conse- 

 quence of a vital attraction, resulting in the manner which we have explained, and ex- 

 erted exterior to and independently of the vessels, and whilst we consider this expla- 

 nation to be supported by the nutritive actions of the lowest animals, yet we would by 

 no means exclude the influence of that part of the ganglial nerves distributed to the ca- 

 pillaries, from a part in the operation, more especially in the higher classes of animals. 

 Indeed it seems difficult to suppose which of those in the higher animals namely, 

 whether the nervous globules distributed to the simple textures, and placed beyond 

 the capillaries, or those constituting the nervous fibrilhe which surround them, 

 are most efficient in the nutritive process. An intimate view of the subject would 

 suggest, that in man and the more perfect animals, the latter organization is the 

 more active of the two iu the operation in question ; and that the capillary vessels, in 

 consequence of the ultimate nervous structure which surrounds them, and of the vital 

 influence which this structure exerts, secrete from the fluid circulating in them certain 

 materials in a similar manner to that in which they perform the other secretions in se- 

 creting organs, and by means either of appropriate vessels or pores. 



As it has been shown that the blood consists of minute globules, or corpuscles sur- 

 rounded by a coloured envelope circulating in a ma'ss of fluid, and that the simple solids 

 of the body are constituted of similar corpuscles, in a state of intimate or vital attrac- 

 tion, as those of the blood, when they ai-e separated from the envelopes, so it may be 

 inferred, that a part of the function which the ultimate distribution of the ganglial 

 nerves perform on the capillary vessels, is to secrete similar corpuscles, from the blood 

 circulating in them, to that which the texture possesses in which the operation takes 

 place ; and that this having been accomplished, the vital attraction is preserved either 

 by means of the influence with which these corpuscles are endowed, as a consequence 

 of the previous process of animalization which they have undergone, or of the influence 

 exerted upon them after they leave the vessels by the nervous globules and fibrillas 

 disseminated in the textures, or perhaps by both species of vital action, either the one 

 or the other acting more or less* partially according' to the nature of the particular tex- 

 ture in which the process takes place, and according to inappreciable and fortuitous 

 causes. 



Hence it will be perceived that nutrition is essentially a vital operation, that it is 

 placed under the control of the extreme ramifications of a particular system, to which 

 we have referred all the vegetative or organic operations which characterize the ani- 

 mal kingdom ; that it is performed in all animals except the very lowest, through the 

 medium of circulating organs, and in the highest, as a consequence of certain prepara- 

 tory processes ; that it requires in man and in the higher animals a capillary circulation 

 for its performance, but that neither of the capillary apparatuses which have been con- 

 tended for is sufficient of themselves to accomplish it, although the most simple of 

 them under the dominion of the vital influence of that particular structure which we 

 find every where disseminated where there is life, is all that is requisite as the material 

 instrument of the process ; and lastly, and as a consequence of the foregoing position* 

 that nutrition is modified, controlled, increased, or even annihilated, either generally 

 or in particular parts of the body, by the state of the vital influence allied to the mate- 

 rial organization, to which we have already imputed it, according as this particular or- 

 ganization in its centres and ramifications throughout the animal frame is generally or 

 locally affected. 



Of the Dedication of the Optic Nerves, 



Vicq D'A.zyr, found, on examining with the microscope, an horizontal section of the 

 optic nerves of the human subject, after it had been hardened in alcohol, that the me- 

 dullary fibres occupying the exterior side of the optic nerve, proceed in a direct man- 

 ner from the optic thalamus to the eye of the same side ; and that the place of union 

 presents a homogeneous tissue The Wenzels came nearly to the same conclusion 

 from their observations, but remarked, in addition, that while the fibres of the exterior 

 side of the nerve go immediately to the eye of the same side, those fibres, placed in its 

 interior side of the nerve go immediately to the eye of the same side, those fibres, 

 placed in its interior sid^, are directed obliquely towards the other nerve, without, 



