454 PROGRESS or VETERINARY science and art. 
M. St. Cyr first mentions the effusion of plastic lymph, 
and its coagulation, glueing all the parts around the vein, 
but not infiltrating the whole of the venous tunics. It is only 
the outer cellular coat that is involved ; so that the middle 
elastic and contractile one, though itself modified and thick- 
ened in consequence of inflammatory action, is not glued to 
the surrounding fibro-cellular tissue, but is readily stripped 
from it. The middle coat acquires that firmness which 
prevents the collapse of the vein when the latter is emptied. 
The ecchymotic specks of the internal serous lining are not, 
says St. Cyr, cadaveric, but constitute a special anatomical 
character of inflammation of the serous membrane which 
is never vascularized.* 
At the same time as the above lesions are forming, con- 
centric layers of lymph are gradually deposited within the 
vein — such deposit is of slow progress, and, a long while after 
its commencement, the vein is generally still permeable to 
blood. The lymph is the decolorized liquor sanguinis of 
blood as it coagulates, and the coagulation occurs either 
in concentric layers, or the cylindrical layers are incomplete, 
and at the point of interruption is a groove or channel 
left; the latter appearance occurs when the first layer of 
coagulated blood does not extend all round the interior of 
the vein. Lastly, St. Cyr speaks of a discoid deposition of 
fibrin as the result of a plug completely closing the vein at 
the spot where active inflammation has set in. The blood 
above the seat of occlusion then coagulates progressively 
from the plug towards the nearest collateral branch, so as 
to acquire the appearance of superimposed solidified lymph 
discs.f 
When the blood first clots in the vein it is only adherent 
by its inferior extremity, and is mostly loose and floating. It 
soon adheres completely. The discoloration of the clot 
extends not always from the centre to the periphery, but from 
the oldest portions. Where the layers are concentric and 
tubular, they lose their colour first in the centre, and then 
towards the circumference. 
Inflammation may subside, and the whole of the lesions 
described disappear. Some authors say, that once the blood 
has clotted wdthin the vein, the latter is never restored, whereas 
others believe that a vein absolutely impervious to blood, 
* I presume St. Cyr here means, that it is never the seat of ramified 
redness. 
f For the sake of rendering this clear, I would compare it to the filling 
the veins with flat pieces of lymph, like shillings, but capable of adhering to 
the parietes of the vein, and to each other. 
