NUTRITION. 



749 



from the blood vessc Is", and its subsequent con- 

 solidation in the manner already described. 

 No such idea seems to have occurred to the 

 continental physiologists, who, following in the 

 path which had been marked out by Schwann, 

 have sought to trace, for all the tissues, an imme- 

 diate origin in cells. But the writer does not hnd 

 that any of them are sufficiently aware of the 

 facts already detailed, in regard to the definite 

 structure which tibrin will assume, when it has 

 undergone a high degree of elaboration, and has 

 coagulated under the most favourable circum- 

 stances ; and with the greatest respect to their 

 authority, he ventures to attach sufficient weight 

 to the observations of Messrs. Gulliver and 

 Addison, confirmed as they are by his own, to 

 induce him to adopt a different explanation, 

 which he offers with diffidence, to be confirmed 

 or set aside by future enquiries. 



The fibrous tissue existing in false mem- 

 branes, and still more that which has been dis- 

 covered by the writer in the egg-shell, may be 

 regarded in his opinion as a type of those sim- 

 ple fibrous tissues, which form a large porpor- 

 tion of the bulk of the body in the higher 

 animals, and of which the function is purely 

 mechanical. When we contrast the fabric of 

 an animal with that of a plant, we are struck 

 with this important difference in their conform- 

 ation, that whilst the latter is made up solely 

 of elements which are to perform their several 

 parts in the performance of the nutritive and 

 reproductive operations, (the only exception 

 being in the case of those more solid portions 

 of the fabric which are destined to give 

 mechanical support to the remainder), the 

 former is composed of a much greater variety 

 of parts, which are adapted to move upon each 

 other. Now this purpose requires, not only 

 the addition of certain new tissues, to which 

 nothing analogous is to be found in plants, for 

 creating and exercising the motor power, but 

 also an adaptation of the whole structure to this 

 new condition. The tissues of plants entirely 

 consist of cells, or simple modifications of them. 

 Some of these cells being strengthened by in- 

 ternal deposits, form the solid woody frame- 

 work of the stem and branches, which gives 

 support to their wide-spreading foliage and 

 numberless blossoms. Others coalesce, by the 

 disappearance of their intervening partitions, 

 into tubes, which serve for the conveyance of 

 fluid between the most distant parts. But the 

 great bulk of the fabric still consists of cells, 

 closely adherent to each other, and actively par- 

 ticipating in the various operations of organic 

 life. In like manner in the animal body, a 

 certain part of the cells have contributed to form 

 the solid osseous and cartilaginous framework, 

 which not only gives support and protection to 

 the body, but contributes to its power of move- 

 ment, by affording fixed points for the attach- 

 ment of its muscles. Others again have coal- 

 esced into vessels, as in plants, for the rapid 

 conveyance of fluids. Others, too, after a simi- 

 lar coalescence, have developed new and re- 

 markable products in the interior of the tubes 

 thus formed, and become transformed into those 

 nervous and muscular tissues, to which nothing 



analogous is found in plants, and which are the 

 peculiar instruments of animal life. Yet still 

 there remains a large number of unchanged 

 cells scattered through the body, which perform, 

 as in plants, the essential part in the functions 

 of nutrition, reproduction, &c. These, how- 

 ever, could not be held together in their con- 

 stantly-varying relative positions without some 

 intervening substance altogether different from 

 true cellular tissue. It must be capable of 

 resisting tension with considerable firmness and 

 elasticity ; it must admit free movement of 

 the several parts upon one another ; and it must 

 still hold them sufficiently close together to 

 resist any injurious strain upon the delicate 

 vessels, nerves, &c., which pass from one to 

 another, as well as to prevent any permanent dis- 

 placement. Now all these offices are performed 

 in a remarkably complete degree, by the ureolur 

 tissue,* the reason of whose restriction to the 

 animal kingdom is thus evident. It is chiefly 

 composed of interlacing fibres and shreds of 

 membrane, which do not seem possessed of any 

 other than simply physical properties; the small 

 degree of vital contractility which it possesses 

 in some spots (as in the dartos,) being attribut- 

 able to the intermixture of fibres analogous to 

 those of the unstriated muscular tissue. One 

 of its most remarkable peculiarities is the ra- 

 pidity of its regeneration ; and this is obviously 

 due, in part, to the large amount of bloodvessels 

 by which it is traversed. The accounts given 

 of its developement by Schwann and Henle do 

 not by any means correspond ; and it appears 

 to the writer, that the evidence of the partici- 

 pation of cells in the process, in any other way 

 than as elaborating the fibrin, is very insuffi- 

 cient. The observation already quoted from 

 Mr. Addison ( p. 746) seems to explain some 

 appearances occasionally met with, which in- 

 duced those observers to assign a more direct 

 cell-origin to this tissue; for he notices that the re- 

 mains of the white corpuscles, and little aggrega- 

 tions of the granules they had emitted, seemed 

 to be the centres, as it were, of the fibrillation.f 

 If we once admit this doctrine in regard to 

 areolar tissue, it is not difficult to extend it to 

 those fibrous structures in general, which re- 

 semble it in the physical natuie of their func- 

 tions; and we shall then leave to the tissues of 

 cell-origin, in animals as in plants, the perform- 

 ance of those operations which must be re- 

 garded as vital in their character. As an ad- 

 ditional argument in support of this view, the 

 appearances presented by the semi-fibrous car- 

 tilages may be adduced. In the cartilages of 



* This was formerly termed CELLULAH tissue, 

 under which designation it is described in the pre- 

 sent work ; but the appellation here given is the 

 one under which it is now generally spoken of, for 

 the sake of distinguishing it from tissues really 

 composed of cells. 



f Since writing the above, the author has become 

 aware that a view of the developement of areolar 

 tissue, essentially corresponding with that advanced 

 aliove, has been recently put forth by Maudl, 

 (Manuel d'Anatomie Generate, p. 552,) although 

 he too seems quite unaware of the degree in which 

 the fibrinous part of the blood Jibrillates in coa- 

 gulating. 



