56 DR DAVY’S OBSERVATIONS ON BLOOD AND MILK. 
3. On the Tendency of Fibrin in Coagulating to a certain arrangement of its 
Particles. 
Amongst the many remarkable properties of coagulable lymph, I am not 
aware that a tendency of its particles to arrange themselves in a certain manner 
out of the body, representing, as it were, what takes place in the body in the 
process of growth and of reparation, has hitherto come under observation, or, at 
least, has been the subject of commentary. 
A striking instance of the kind I have witnessed in the buffy coat. When 
the buffy coat is well marked, as in cases of acute rheumatism, when it is thick 
and cupped, the blood abstracted having been slow in coagulating, it is easily 
detached from the soft crassamentum ; and this is best done under water. Thus 
separated, it may be described as a fibrous mass loaded with serum, enveloped in 
a pellicle or membrane, performing the part of a sac. This pellicle, or containing 
membrane, is very thin, yet of considerable strength, and with care may be dis- 
sected off, especially after maceration in water for two or three days, at a low 
temperature. It is very like a serous membrane, both as seen with the naked 
eye, and under the microscope. Under the latter, it bears a strong resemblance 
to the arachnoid, appears as a tissue of extreme delicacy; hyoloid, without any 
visible pores or fibres, with a few particles like blood corpuscles, or their remains 
(according to the method used of separating it), scattered through it. Whena 
force is applied to it, it breaks less readily in one direction than another; and 
exhibits, when drawn in one direction, more elasticity than in the opposite. When 
the blood, as is usual, has been received in a circular vessel, and the buffy coat, 
of course, is of the same form, tearing the membrane with a forceps towards the 
margin, shreds of it, several lines in length, are easily detached in a line from 
the centre to the circumference, but not in a line at right angles to this; and in 
the same direction small portions of the membrane exhibit considerable elasticity, 
which they do not in the opposite direction. 
I may mention another example, also well marked. If the blood, in the act 
of coagulating, is stirred with a glass rod, or a wooden skewer, or the like, the 
fibrin, as it is well known, will adhere, with which blood corpuscles will be mixed. 
The adhering clot, consisting of the two, the fibrin in excess, when pulled off, 
which it easily is, exhibits a canal with a smooth inner surface. If it be well 
washed to deprive it of colouring matter, and slit open, it will be found to bear a 
close resemblance to an artery, especially to its middle coat, being composed of 
fibres arranged seemingly transversely, that is, at right angles to the axis of the 
tube. This is to be inferred from the effect of a force applied. If applied in that 
direction, transverse shreds pretty readily separate; but if in the opposite direc- 
tion, using a forceps, only small bits. And, in the one, the transverse direction, 
