192 ON THE ELEMENTARY PARTS OF THE HUMAN FABRIC. 



repair of injuries, lead to precisely the same conclusions. The first appear- 

 ance of the vascular network in the newly-forming tissue, is in the form of 

 transparent arborescent streaks ; which push out extensions on all sides ; these 

 encounter one another, and form a complete series of capillary reticulations, 

 some of which come into connection with the vessels of the surrounding parts. 

 According to the observations of Mr. Travers,* isolated corpuscles enter these 

 newly-formed capillaries, and perform an oscillating movement in them for 

 some hours, before any series of them passes into it ; so that we cannot re- 

 gard the new channel as burrowed out by a string or file of red corpuscles, 

 pushed forth from the nearest capillary by vis a tergo, as some have main- 

 tained. 



11. Compound Tubular Tissues. 



223. There now remain to be described two elements of the Animal fabric, 

 to which there is scarcely anything that bears the least analogy in the struc- 

 ture of Plants ; namely, the Muscular and Nervous tissues. We have seen 

 that, putting aside the Simple Fibrous tissues, whose function is purely me- 

 chanical, the Animal fabric, so far as we have yet passed its elements under 

 review, is constructed upon the very same type with that of Plants ; all the 

 parts actively concerned in the processes of nutrition, secretion, reproduction, 

 &c., retaining their original cellular character ; the vessels that serve for the 

 conveyance of fluid, having their origin in cells, whose cavities have coalesced ; 

 whilst the more solid portions of the frame-work are made up of united cells, 

 whose cavities are occupied by internal deposit. Now the purpose of the 

 Muscular and Nervous system is entirely different. The former is the one, 

 by which all the sensible movements of the body are immediately effected ; 

 and it is only amongst a small number of Plants, that any such movements 

 are exhibited. The latter serves as the instrument by which sensations are 

 received ; and by which the instincts, emotions, or volitions, excited by these 

 sensations, act upon the muscles : a class of functions which we have no 

 reason whatever to regard as performed by Plants. In fact, as already pointed 

 out ( 1 4), the distinction between the two kingdoms is more properly 

 founded upon the presence of these functions and of their instruments in the 

 Animal, and upon their absence in the Plant, than upon any other structural 

 character. 



224. Now it might have not been unreasonable to expect, that tissues alto- 

 gether so dissimilar in their properties, and in the purposes to which they are 

 destined, should have a structure departing widely from the type of the simple 

 Cell. Yet it does not appear that this is the case. That portion of the Nerv- 

 ous matter, by which its most active functional changes are effected, retains 

 its original cellular character without alteration ; and the so-called fibres, 

 which constitute the Nerve-trunks, and which convey the influence of these 

 changes, are in reality tubes, formed as it would seem by the coalescence of 

 a linear series of cells, and chiefly distinguished by the peculiar nature of 

 their internal deposit. In like manner, we shall find that the ultimate Mus- 

 cular Fibre is also a tube, formed out of the same elements, and distinguished 

 by the nature of its contents ; which, in the most perfect form of the tissue, 

 are composed of linear series of extremely minute secondary cells. 



225. Muscular tissue exists under two forms ; one in which the ultimate 

 fibres are marked by transverse striae ; and the other in which they are plain 

 orunstriped. The former is chiefly employed in performing the various move- 

 ments, which are effected through the agency of the Nervous system, and which 



* Physiology of Inflammation and the Healing Process. 



