OF THE ELEMENTARY SOLIDS. 3 



Of the Nervous System in the Lower Animals. 

 Note B. 



The lowest order of animals, as the Polypi, &c. has usually been" considered to be 

 destitute of a nervous system. This, however, is not the case. If we look narrowly 

 into the structure of the lower animals, we shall find that even the lowest offer traces of 

 a nervous system : and as we rise through the scale of the animal creation, we shall find 

 this system becoming more and more perfect in its state of existence, and presenting ap- 

 pearances of perfection in proportion to the number and extent of functions which the 

 animal is capable of exerting. Even the Polypus, the lowest of the animal kingdom, 

 seems to possess a nervous system, in the simplest state of existence. If this apparently 

 homogeneous animal be examined with a powerful microscope, numerous globules, en- 

 tirely resembling those seen in the nervous system, appear disseminated throughout its 

 structure. As a result of this simplicity of conformation, it presents no perfect manifes- 

 tation of sensibility and contractility. It is not constituted ot separate textures and 

 organs destined to perform specific purposes ; and, consequently, as no relation or band 

 of union is requisite between its parts, as in those animals which have particular organs 

 or structures which perform, particular offices ; and as each of its individual parts per- 

 forms the functions of the whole animal, so its nervous system is disseminated through- 

 out its structure, without being arranged into cords of communication or centres of re- 

 inforcement as in those animals, which, endowed with distinct organs and perfect func- 

 tions, possess both. 



As we rise in the scale, on the contrary, we perceive,in the more perfect and in the 

 highest animals, the intimate texture of the nervous system, arranged so as to form com- 

 municating chords between organs which are distantly separated from each other, and 

 not only are they provided with these, but each viscus frequently possesses in addition 

 a separate nervo'us centre, on which the functions performed by that viscus depend : 

 whilst the former arrangement is calculated to preserve a reciprocity of action a mu- 

 tual dependence of parts and of functions, the latter generates a vital influence, modi- 

 fied in kind and in degree to the part which it actuates, which influence, in conjunction 

 with what the organ may receive'from a common centre, and what may be generated in 

 the nerves of its own structure,- is exerted in the production or the functions of which 

 the conformation of the organ is but the mechanical instrument. Thus the vital in- 

 fluence is furnished to the different viscera in proportion to, and suitably with the na- 

 ture of, its expenditure in the more complex and more complete exertion of the opera- 

 tions which each of them is destined to fulfil. 



Respecting this subject, therefore, the following propositions may be stated : That 

 corpuscles or globules, entirely similar to those of which the nervous system is com- 

 posed, according to the observations of Prochaska, the Wenzels, Bauer, and Edwards, 

 are found desseminated, without any regular order, throughout the apparently homo- 

 geneous structure of the lowest order of the animal kingdom : that, as we rise in our 

 observations through the scale of animals, we perceive this dissemination existing only 

 in the mucous structures, and we observe a distinct nervous mass, or masses; am:, as 

 the animal presents separate organs destined- to the vital operationSj so this intimate 

 nervous structure becomes disposed into cords of communication, each organ possess- 

 ing in addition the higher that we ascend in the scale more especially a detached 

 but dependent mass of reinforcement, which varies in form, appearance, and connexion 

 with -other organs, or with other parts of the same system, according to the functions 

 which it is destined to actuate. 



Of the Primary Solids and Compound Textures of the Body. 

 Note C. 



The intimate or elementary constitution of the animal textures has long engaged the 

 attention of Anatomists and Physiologists. As researches respecting this subject can 

 only be prosecuted by means of the microscope, the result must, therefore, be received 

 with some degree of reservation, unless they coincide with the observations of former 

 inquiries, or be confirmed by subsequent observers, From amongst those who have 



