PHLEBITIS AND THROMBOSIS. 3605. 
It has been tried to explain thrombosis in the various circumstances . 
where they take place, either by an alteration of the blood or a-change in 
the structure of the venous wall. And again, successively were suspected the: 
excess of fibrin in the blood (hyperinosis), the exaggeration of its coagul- 
ability (inopexia), the qualities of the serum, the excess of white globules, 
the abundance and abnormal viscosity of the hematoblasts,—and at last 
the simultaneous interference of several factors: such as a mechanical. 
disturbance in the venous circulation, in the diminution in the bloody 
current, or in analteration of this fluid. But none of these influences.. 
has, from the point of view of the production of thrombosis, the impor- 
tance that is offered by the condition of the venous endothelium. The 
diminution or even the arrest of the circulation through a vein do not give - 
rise to thrombosis, if the endothelium is perfect in its integrity. ‘ Blood has. 
been kept in a venous segment, between two ligatures, during several hours, 
even several days. On the contrary, as soon as the slightest alteration occurs. . 
on the endothelial surface (for instance, in striking the external face of 
the vein with a forceps), immediately clots are formed on the diseased 
spot, as it takes place round a foreign body introduced in the vessel ’” 
(Quénu). That which dominates in the formation of thrombosis, is the - 
alteration of the venous endothelium. 
Bacteriological researches have shown this alteration in cases where the - 
naked eye examination would not permit it. Some thrombosis reputed 
primitive have at last been recognized as secondary, of infectious nature, . 
promoted by micro-organisms. Spontaneous thrombosis, so called, is most : 
often but an attenuated form of phlebitis. ‘Between thrombosis called _ 
spontaneous and suppurative phlebitis, there is only a difference of degree 5. 
the lesion is the same, the cause is identical.” 
In its turn, the theory of Virchow had to give its place to the micro-- 
bian. “This new doctrine considers some thrombosis (if not all) as of in- 
fectious nature; it rests on severe observations and the presence, on the - 
inside of thrombosed veins, of pathogenous micro-organisms ; it brings us . 
back to the conception of primitive phlebitis, anterior to the clot; it adds. 
a pathogenous notion of great value, viz: that this phlebitis recognizes for-- 
cause the action, upon the living endothelium, of a microbian agent’” 
(Quénu). 
Phlebitis is specially common on veins where bleeding is performed, im 
particular, in the jugular of horses, and the subcutaneous abdominal in. 
bovines. Umbilical phlebitis, frequent and dangerous in young subjects of” 
all classes, shall be studied later on, in the chapter on Arthritis of Young~ 
Animals. 
There are several varieties of phlebitis. They are divided into super. 
ficial and deep, internal and external, traumatic and spontaneous, infec—. 
