: 
| 
| . 
_ from the bloodvessels, 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 
th which had been marked out by Schwann, 
ave sought to trace, for ad the tissues, an imme- 
diate origin in cells. Butthe writer does not find 
that any of them are sufficiently aware of the 
facts already detailed, in regard to the definite 
: structure which fibrin will assume, when it has 
__undergonea 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 
productive operations, (the only exception 
ing in the case of those more solid portions 
C e 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 
ing and exercising the motor power, but 
9 an adaptation of the whole structure to this 
y condition. The tissues of plants entirely 
nsist of cel/s, or simple modifications of them. 
me of these cells being strengthened by in- 
deposits, form the solid woody frame- 
“work of the stem and branches, which gives 
“Support to their wide-spreading foliage and 
“humberless blossoms. Others coalesce, by the 
- dise ce of their intervening partitions, 
‘Into tubes, which serve for the conveyance of 
fluid between the most distant parts. But the 
reat bulk of the fabric still consists of cells, 
ly adherent to each other, and actively par- 
ating in the various operations of organic 
fife. In like manner in the animal body, a 
certai oth the cells have contributed to form 
the solid osseous and cartilaginous framework, 
Which not only gives support and protection to 
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- 
ar coalescence, have developed new and re- 
markable products in the interior of the tubes 
hervous and muscular tissues, to which nothing 
| 
NUTRITION. 
thus formed, and become transformed into those 
749 
analogous is found in plants, and whichare 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 areolar 
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 ofits 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 insufti- 
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.+ 
If we once admit this doctrine in regaid to 
areolar tissue, it is not difficult to extend it to 
those fibrous structures in general, which re- 
semble it in the physical nature 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 CELLULAR 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. 
+ Since writing the above, the author has become 
aware that a view of the developement of areolar 
tissue, essentially corresponding with that advanced 
above, has been recently put forth by Mandl, 
(Manuel d’Anatomie Générale, p. 552,) although 
he too seems quite unaware of the degree in which 
the fibrinous part of the blood fibrillates in cva- 
gulating. 
\ 
