IQQ ON MUSCULAR MOTION^. 



favour the probability, that the medullary matter of nerves is 

 formed at the parts where it is required, and not in the prin- 

 cipal feat of the cerebral medulla. 

 WhJjthetthe This dottrine^ clearly ellabliflied, would lead to the belief 



matter of nerve ^p ^ ^ extended commixtiire of this peculiar matter in all 



be not exten- , , . 



lively mbxed in the (entible and irritable parts of animals, leaving tbe nerves 



alhrntableparts.jp their limited diftribution, the fjmple office of conveying im- 

 preffions from the two lentient malles with which their ex- 

 tremities are conneded. The moft fimple animals in whom 

 no vifible appearances of braih Or nerves are to be foundi and 

 no fibrous arrangement of mufcles, may be confidered of this 

 del'cription : Mr, John Hunter appeared to have had fome 

 incomplete notions upon^ this fubjecl, which *rinay bfe gathered 

 from' I) is reprefentation of a materia vifce in his Treatife on the 

 Blood, &c. Perhaps it would be n)ore proper to diftinguilh 

 ihe peculiar matter of mufcle by fome fpeeih<e (ermv fuch, fo» 

 example, as materia contraBilis^ ' ' • ' "■ 



PecwTiar adapta- . A particular adaptation for the nerves which fupply the 



tion for the electrical batteries of the torpedo, and srymnotus, isobfervable 

 nerves of electric . , . . 



iniaia's. ©" the exit of each from the Ikull ; aver which there is a firmt 



cartilage a6ting as a yoke,^^ with a m^ifcle affixed to it^ for th^ 

 obvious purpofe of compreffion : fo that a voluntary mufcle 

 probably gaverns the operations of the battery, 



Tbe matter of the nerves,- 0nd brain, is very fimilar in alt 

 ijie djiferent clalTes of animab* 



. The external configuration of animals is not more varied 

 than their internal (Iructure. 

 ConBguratlon Tiie bulk of an animal, the limitation of its- exiftence, the 

 and (truaure of j^j^jj^jj^ in which it lives, and the habits it 'b defined to 

 cialfe« 5f ani- purfue, are each, and all of them, lb many indications of the 

 mals^ complexity or limplicity of their internal liruClure. It is 



notorious that the number of organs, and of members^ is varied 

 in all the different claifes of animals; the vai'cular and nervous- 

 fyfteras> the refpiratory, and digeftive organs,, tlie parts for 

 procreation, and the inllruments of motion, are feveraJly varied,. 

 Very fimple anl- and adapted to the condition of the fpecies. Thi^ modification 

 "^*''* of anatomical flru6ture is extended in the loweft tribes of ani- 



mals, until the body appears to be one homogeneous fubflance. 

 The cavity for receiving the food is indifferently the internal^ 

 or external furface, for they may be inverted, and ftill con- 

 tinue 



