748 
Haller ; but it has been generally overlooked 
by subsequent physiologists, until attention was 
drawn to it by the enquiries of Messrs. Addison, 
Gulliver, and others. It is in the buffy coat, 
however, that the fibrous arrangement is best 
seen; On account, as it would appear, of the 
stronger attraction which the particles of fibrin 
have for one another, when its vitality has been 
raised by the increased elaboration to which it 
has been subjected. That there are varieties of 
plasticity in the substance, which, on account 
of its power of spontaneously coagulating, we 
must still call fibrin, appears from this fact 
among others,—that, in tuberculous subjects, 
the guantity of fibrin in the blood is higher 
than usual (Andral and Gavarret), although its 
plasticity is certainly below par. It is easy to 
understand, that its plasticity may be increased 
as that it may be diminished ; and this either in 
the general mass of the blood, or in a local de- 
posit In fact, the adhesions which are formed 
y the consolidation of coagulable lymph,—or 
in other words, of liquor sanguinis, whose plas- 
ticity has been heightened by the vital actions 
of the white corpuscles in the capillaries of the 
part on which it has been effused,—often 
acquire very considerable firmness, before any 
vessels have penetrated them ; and this firmness 
must depend upon that mutual attraction of the 
particles for one another, which in aplastic de- 
posits is altogether wanting, and which in 
caco-plastic deposits is deficient. A very inte- 
resting example of a structure entirely composed 
of matted fibres, and evidently originating in 
the simple consolidation of fibrin, has lately 
been discovered by the writer. This is found 
in the membrane adherent to the interior of the 
egg-shell (membrana putaminis); and also in 
that which forms the basis of the egg-shell itself. 
Between the two, there is no essential difference; 
as may be seen by examining “ an egg without 
shell,” as it is commonly termed, (or rather one 
in which the shell-membrane has been uncon- 
solidated by the deposition of calcareous matter) ; 
or by treating the egg-shell with dilute acid, so 
as to remove the particles of carbonate of lime, 
which are deposited in the interstices of the net- 
work. The place of the shell is then found to 
be occupied by a membrane of considerable 
firmness, closely resembling that which sur- 
rounds the albumen of the egg, but thicker and 
more spongy. After maceration for a few days, 
either of these membranes may be separated 
into a number of lamine, each of which (if suf- 
ficiently thin) will show the beautiful arrange- 
ment of reticulated fibres, which is delineated 
in the accompanying figure (fig. 405). It is 
impossible to refuse to such a structure the desig- 
nation of an organised tissue, although it contains 
no vessels, and must be formed by the simple 
consolidation of fibrin, poured out from the lining 
membrane of the oviduct of the bird. It is 
probably in the same manner, that the chorion 
of the mammiferous animal originates; since 
this is a new envelope, formed around the ovum, 
during its passage along the Fallopian tube. In 
the latter, for an ulterior purpose, vessels are 
afterwards developed, by extension from the 
contained ovum; and by the nutrition they 
NUTRITION. 
“os 
gy 
supply, its size is increased, and changes 
place in its texture. But in the mem brat 
of the bird, there is no need of 3 because 
no subsequent change in its texture is required, 
and its duration is sufficient for the purpose it 
has to answer. ae 
In all these instances, the fibrillated structure 
contains a certain amount of corpuscles, which 
lie in the meshes of its network. These ha 
been termed “ exudation-globules” by some 
authors,-—by others “ organie germs,”"—and_ b 
others (especially Mr. Addison) are regarded as 
identical with the white corpuscles of th 
blood. They may present considerable varie 
ties in size and appearance; having in som 
instances the characters of fully-formed cells 
whilst in others they rather resemble nuclei ' 
aggregations of granules. It seems difficult t 
believe, that they can be identical with the wh 
corpuscles of the blood ; since if the exudati 
has been poured forth by open orifices, suf 
ciently large to admit these to pass, there wou 
be no obstacle to the escape of the red corpus 
cles,—at least where the latter are of bly. 
size, asin mammalia. They are — 
be regarded as originating in the fibrinous ¢ 
posit, from germs which it contained, whe 
effused from the vessels; of which germs 
white corpuscles may have not improbab 
been the parents. The degree of their dev 
lopement into pie pea ap - re lepe 
upon the degree of plasticity o depo 
Not unfrequently hey seem arrested in 
progress ; especially in cases where the ex! 
tion verges towards a pena charac 
In the egg-membrane, very of these | 
puscles are seen; and as it is thus alt 
entirely composed of consolidated fibrin 
possesses considerable toughness. The § 
1s the case with highly plastic exudations 
inflamed serous surfaces. But in de 
which are less plastic, we see a larger numb 
these corpuscles, and a diminution and 
creased tenacity of the fibres; the meml 
then becomes quite friable, and approach 
character of a purulent exudation. The 
plastic deposits will be presently notice 
der the head of Abnormal States of Nut 
At present we shall proceed to consider 
application of these facts to the ordinary 
ditions of that process. : 
The question naturally suggests itse 
limine, whether any of the tissues of the at 
body are formed by the simple effusion of 
* 
f f 
J 
- 
a 
