NUTRITION. 
smaller fragments, however roughly or strongly 
the two pieces of glass be made to rub against 
each other. This is a ‘glaring instance’ of a 
compact, tough, elastic, colourless, and fibrous 
tissue, forming from the colourless elements of 
the blood ; and the several stages of its formation 
_ may be actually seen and determined. Nu- 
merous corpuscles may be observed, in all these 
ae to have resolved themselves, or to 
ve fallen down into a number of minute 
molecules, which are spread out over a some- 
what larger area than that occupied by the 
entire corpuscles; and although still retaining 
a more or less perfectly circular outline, yet 
refracting the light at their edges, in a manner 
very different from that in which the corpuscles 
themselves are seen to do. It is from these 
and various other larger and more irregular 
masses of molecules on disintegrated corpuscles, 
that the fibrinous filaments shoot out on all 
_ sides, as from so many centres ; or frequently 
_ the filaments are more copious in two opposite 
directions.” * 
A different view of the cause of the produc- 
tion of fibrin, however, has been entertained by 
“some eminent physiologists; and it does not 
seem right to allow the opinions of Wagner, 
‘Henle, and Wharton Jones to pass without 
_ notice, even though they appear to the writer 
to be easily set aside. By these observers, the 
elaboration of fibrin has been attributed to the 
red corpuscles, and has been regarded as one, 
‘at least, of their special functions. Nearly all 
— 
4 . 
assign this duty to the white corpuscles, tell 
equally against the doctrine now under con- 
Sideration. The presence of fibrin in the circu- 
_ lating fluid may be regarded as a universal fact ; 
_ but the red corpuscles are restricted to verte- 
_ brated animals : how, then, is the plastic element 
elaborated in the invertebrata? The number of 
_ red corpuscles in the blood of different classes 
bears an obvious relation to their amount of 
respiratory power, and to the functional activity 
of the several organs, which is closely connected 
_ with the amount of oxygen introduced into the 
_ system; but it does not bear the same relation 
with the activity of the formative processes, 
_ which may be taking place energetically (as in 
_ the developement of the embryo, or in the re- 
paration of parts in the adult) in a state of 
functional quiescence. That the proportion of 
d corpuscles in the blood had a special rela- 
ion to the nervous and muscular energy of an 
_ animal, and to the amount of oxygen consumed 
by it, has long ranked as a physiological truth ; 
‘and the opinion has been gradually gaining 
ground, that although the liquor sanguinis is 
‘undoubtedly affected in a considerable degree 
by exposure to oxygen in the respiratory capil- 
-laries, the red corpuscles are the special agents 
'y which oxygen is conveyed into the systemic 
pillaries, that it may furnish the conditions 
required for muscular contraction and other 
| functional operations, which depend upon a 
| due supply of arterial blood. In the inverte- 
_ * Transactions of the Provincial Medical Asso- 
ciation, 1843, 
the arguments, however, which have led us to- 
747 
brated animals in general, the amount of respi- 
ration is so low, that this special provision is 
not required. There is an apparent exception, 
however, in the case of Insects, which have no 
red corpuscles, and which yet can display a 
greater amount of animal energy, and which 
consume (when in a state of activity) a larger 
quantity of oxygen in proportion to their size, 
than beings of any other class whatever. But 
here the exception proves the rule ; for the con- 
veyance of oxygen through the tissues is not 
accomplished in Insects by the circulating fluid, 
which has a comparatively sluggish movement, 
but is effected more directly by the ramifying 
trachee, which introduce air into the minutest 
portions of the structure. 
The pathological evidence that the red cor- 
puscles are not the elaborators of the fibrin, 
i to the writer to be quite conclusive. 
hilst the quantity of fibrin is so remarkably 
increased in inflammation, the number of red 
corpuscles undergoes no decided change. 
Again, the augmentation of the fibrin is not in- 
compatible with a chlorotic state of the blood ; 
the peculiar characteristic of which is a great 
diminution in the proportion of red corpuscles. 
By such alterations, the normal proportion be- 
tween the fibrin and the red corpuscles, which 
may be stated as a : B, may be so much altered, 
as to become, in inflammation, 3a : B, in chlo- 
rosis 4:48. Again, in fever, the characteristic 
alteration in the condition of the blood appears 
to be an increase in the amount of red cor- 
puscles, with a diminution in the quantity of 
fibrin; yet if a local inflammation should 
establish itself during the course of a fever, the 
proportion of fibrin will rise ; and this without 
any change in the amount of corpuscles. 
Lastly, the effect of loss of blood has been 
shown by Andral’s investigations to be a marked 
diminution in the number of red corpuscles, 
with no decided reduction in the quantity of 
fibrin, even when this is much above its normal 
standard ; and in this condition of the blood it 
has been observed by Remak that the coleurless 
id Saab are very numerous. 
ormation of tisswe—With the elaboration 
of the alimentary materials into fibrid, the pre- 
paratory processes of nutrition may be regarded 
as terminating ; since the next step is the trans- 
formation of this substance into organised tissue. 
Upon the mode in which this is effected, much 
light has been thrown by recent enquiries ; but 
several points still remain obscure. We shal! 
endeavour, in the following account, to dis- 
tinguish what has been satisfactorily ascertained 
from what is merely hypothetical. 
That the particles of perfectly-elaborated 
fibrin are capable, in solidifying, of spontaneously 
assuming a definite arrangement, cannot now 
be questioned. In the ordinary crassamentum 
of healthy blood, this arrangement can be seen, 
by examining thin slices under the microscope ; 
especially after the clot has been hardened by 
boiling. A-number of fibres, more or less dis- 
tinct, may be seen to cross one another; form- 
ing by their interlacement a tolerably regular 
network, in the meshes of which the red cor- 
puscles are entangled. This fact was known to 
