126 



ANIMAL. 



similar in their outward appearance, resemble 

 one another in their intimate structure. 



The tissues that enter into the composition 

 of animals are much more numerous than those 

 of vegetables. The most universally distributed 

 of these in the more perfect species of animals 

 are the cellular, the vascular, the nervous, and 

 the muscular, to which must be added the 

 tendinous or fibrous, the osseous, the cartila- 

 ginous, and the horny, which are less uniformly 

 diffused among the individuals composing the 

 animal kingdom. 



The cellular is the tissue the most universally 

 encountered among animals; it is demonstrable 

 from the very lowest to the very highest. Its 

 general appearance is that of a soft, homo- 

 geneous, whitish, semi-transparent, extensible, 

 and during life slightly contractile substance. 

 It is permeable to air and liquids, and is easily 

 distended by either of these, when it forms a 

 series of continuous cavities or cells, strangers 

 at first to its constitution, but so readily pro- 

 duced as to have given the tissue its distin- 

 guishing title. The cellular tissue is dispersed 

 abundantly through every part of the animal 

 body ; it enters as a principal element into the 

 composition of many other tissues; it pervades 

 the innermost parts of almost all organs, and in 

 a modified shape forms a covering for them 

 externally ; it may be said to constitute the 

 frame-work of the organs generally, supporting 

 them in their particles as it does in their masses ; 

 it connects them together also, includes and 

 accompanies the bloodvessels that supply them 

 with nourishment, fills the intervals between 

 them, and establishes continuity between every 

 part of individual organized beings. The cellu- 

 lar tissue consists of filaments and laminae, 

 mingled and entangled together; the interstices 

 it contains, and which may be blown up into 

 cells, appear to be moistened during life by a 

 thin vapour, or a variable quantity of serous 

 fluid.* 



The cellular substance appears to constitute 

 the element of the various membranes encoun- 

 tered in animal bodies : the fibrous membranes, 

 the skin, the mucous membranes, the serous 

 membranes, and the synovial membranes, are 

 all readily resolvable into cellular tissue ; they 

 in fact appear to consist of this tissue in dif- 

 ferent states of condensation. 



The vascular is another tissue extensively 

 distributed among animals. Three modifica- 

 tions of the vascular tissue have been reckoned 

 by anatomists, occurring respectively in arteries, 

 veins, and lymphatics. 



The third tissue which is peculiar to animals 

 is the nervous. This may be held the most 

 eminently distinctive of this class of organized 

 beings, as it is by its intermedium that they 

 exhibit almost all the faculties which place 

 them so immeasurably above vegetables in the 



* Rudolphi assigns as a distinction between 

 animal cellular tissue and that of vegetables, that 

 the latter exhibits cells of a more or less regular 

 form with firm walls, nothing of which kind exists 

 in the former : Rudolphi Anat. der Pflanzen, S.26, 

 quoted in Tiedemann. Physiologic, Ister Band, S. 

 182. 



scale of creation, and as, generally speaking, 

 they may be reckoned by so much the more 

 perfect as particular portions of this system 

 are more fully developed. The element of 

 the nervous tissue is a soft, whitish, and 

 little consistent substance, composed of mi- 

 nute globules surrounded by a semifluid sub- 

 stance, and connected together by a tissue of 

 cellular membrane of extreme tenuity. The 

 globules are mostly disposed longitudinally, 

 when they form the medullary fibres of the 

 brain ; surrounded by denser sheaths, they take 

 the form of nerves. In all the higher animals 

 at least, two orders of nerves are distinguished, 

 each, however, being intimately connected with 

 the other, the nerves of animal, or, better, of 

 phrenic life, and the nerves of organic or vege- 

 tative life. The nerves of the first order are 

 connected in the higher classes of animals with 

 a brain and spinal cord ; those of the second 

 proceed from small bodies of a reddish grey 

 colour, and irregular shape, named ganglions. 

 The functions of the first take place with con- 

 sciousness, those of the second without this 

 mental phenomenon.* 



The fourth tissue peculiar to animals is the 

 muscular. In several of the very lowest tribes 

 of these, indeed, the existence of this tissue 

 cannot be demonstrated ; yet its actions begin 

 to be manifested at a very low grade in the 

 scale. The element of the muscular tissue is 

 a fibre, on the ultimate constitution of which 

 there have been many disputes. The ultimate 

 muscular fibre would appear to consist of a 

 series of solid globules longitudinally disposed, 

 and connected into larger and larger fasciculi, 

 which at length compose the distinct bundles 

 denominated muscles. Fibrine is the organic 

 element of the muscular tissue. Its peculiar 

 and distinguishing property is its capacity to 

 contract or to become snorter, and to relax again 

 or return in its quiescent state to its first lentgh. 



The muscles, like the nerves, are divided 

 into two classes or orders, the one under the 

 influence of the will, the other independent of 

 it. The texture is different in each of these 

 two orders : in the voluntary muscles, the fibres 

 and bundles of which the peculiar tissue con- 

 sists are very regularly disposed, and generally 

 in straight and parallel lines relatively to one 

 another ; in the involuntary muscles again, the 

 fibres appear of different degrees of density, 

 run parallel or obliquely with regard to one 

 another, are superposed in layers, intermingled 

 and entangled like a kind of felt, &c. 



* Some physiologists have gone so far as to 

 suppose a rudimentary nervous system among 

 vegetables, which would imply consciousness on 

 their parts of their existence. This, at least, is 

 a very doubtful presumption, but we are not with- 

 out abstract arguments which might be adduced in 

 favour of the supposition. How immensely would 

 the sphere in which the bounty of the Creator 

 had displayed itself then appear enlarged ! The 

 number of beings conscious of the joys of exis- 

 tence would be increased a thousand fold ; and it 

 is even delightful to imagine these lower parta- 

 kers of organization with ourselves and animals, 

 also enjoying the light and sunshine, the sequence 

 of day and night, the freshness of spring, and the 

 fulness of autumn. 



