70 APPENDIX. 



mals, chiefly displayed by the muscular structure. Is it from this circumstance, an at' 

 tribute of muscular parts, and the pure result of their confirmation ? One class of physio^ 

 legists answer this question in the affirmative. But irritability has been displayed by 

 the lowest orders of the animal creation, wherein a muscular structure could not be de- 

 tected, even in the parts themselves which furnished the phenomenon, therefore, al- 

 though a property of the muscular fibre it is neither altogether restricted to it, nor is it 

 strictly the result of the organization of the fibre itself. We must, consequently, refer 

 this property to a conformation still more general than the muscular tissue, both as re- 

 spects the whole scale of the animal creation and the organization of individual spe- 

 cies; allowing at the same time, that a particular structure is requisite to the full and: 

 perfect development of this property, but that this structure depends upon a different 

 source from itself for the property which it displays. 



Having arrived at the conclusion that irritability, although a property of muscular 

 parts, is not the result of muscular organization, but is derived from a" different, and 

 more general system, supplying the muscular structure as well as other structures, we 

 must next inquire what this system is. It has been already inferred, from various con- 

 siderations, that the ganglial class of nerves is distributed in different proportions, to 

 the various textures and organs of the body ; that these nerves are similarly distributed 

 throughout all the individuals composing the animal kingdom ; that in some of its or- 

 ders they constitute the only nervous system which the animal possesses : it has also been 

 demonstrated that this class of nerves, in a more or less perfect state of organization, is 

 present wherever irritability is manifested ; that these nerves are the most generally 

 diffused of any the animal tissues ; that no other structure exists but this which can be 

 shown to be present in every species of irritable parts, in all orders of animals ; and, 

 consequently, that to no other source but this cun the property of irritability be as- 

 signed. 



Having inferred that the muscular fibre is only the instrument of contraction, in its 

 more perfect condition, that it performs this function, in consequence of a certain con- 

 formation, und owing to that conformation being endowed by means of another still 

 more generally diffused than itself, and that this property is derived from the ganglial 

 or soft nerves which proceeds either directly or as an envelope to the arteries, to all the 

 tissues of the body we are led farther to infer that the cerebro-spinal nerves are dis- 

 tributed to muscular parts for specific purposes, but that these parts do not derive their 

 innate properties from these latter nerves these nerves merely excite them, or rather 

 are conductors of a stimulus acting on properties which proceed from a different source. 

 We have contended that these properties are not innate, or the consequence of the 

 conformation of the muscular fibre itself; but are derived from a confirmation still more 

 general, which surrounds^ or is otherwise connected with, the muscular fibrils, and 

 that this more general conformation- is the ramifications of the ganglial class of nerves. 

 Conceiving, therefore, that these nerves in their state of ultimate distribution and dis- 

 semination in the texture of the muscle, whether in the form of unarranged globules, 

 or of minute and variously arranged fibrils resulting from the regular distribution of 

 these globules, are the chief source of the property evinced by muscular parts of every 

 denomination, we further conclude that the voluntary or cerebro-spinal nerves do not 

 produce their specific effects on the muscular fibres, 'owing to a nervous fibril being 

 ramified to each muscular fibril, for this does not take place ; nor. do these effects 

 proceed from the direct influence ef these nerves upon the muscular fibril, for the 

 muscular fibre derives its property or faculty of contraction from a source different from 

 itself, and from the voluntary nerves which occasionally excite its contractions ; but 

 that these nerves seem to act directly upon the ultimate distribution of the ganglial 

 nerves of the muscle, which latter nerves bestow on it the faculty of, or the disposition 

 to active contraction, on the application of a stimulus, which faculty all muscular parts 

 possess the former class of nerves conveying to some of these parts only the natural 

 stimulus which induces contraction, or which excites the active exertion of this faculty 

 bestowed on these parts from a different source, namely, from the glangial system. The 

 mode of termination which the voluntary nerves observe in muscular parts, also favours 

 the opinion which we have now given. These nerves terminate, as we have already 

 noticed, in such a manner as kads us to inter, that they become, in a manner gradually 

 indentified or amalgamated, in the textures which they supply, with the ultimate distri- 

 butions of the ganglial nerves : and the history of the embryo, and the progressive ner- 

 vous development of the lower animals, would dispose us to believe that the voluntary 

 nerves originate in the textures to which they are ramified, from the ganglial system, 

 and that the larger branches of these nerves, the spinal marrow, and encephalon are 

 succc '^s : \v j Y formed. 



