176 VETERINARY SURGICAL THERAPEUTICS. 
-contused wounds ; most commonly, it has as starting point severaf 
‘external phlegmasias related to some infection and carrying with itself 
_gangrenous or necrotic lesions (aphthous fever), The same thing occurs 
in small ruminants. In dogs, its ordinary causes are complicated 
fractures, crushings, and other traumatic lesions of the bones of 
the extremities. In young animals of any species, more especially 
-colts and calves, it is almost always due to the suppurative inflam- 
-mation of the umbilical vein, p//editis of the cord. 
Its etiology consists in the existence of a suppurating trauma, several 
-conditions, however, inherent in this, in the wounded subject, and in 
‘the surroundings, promote its development ; these are especially: the 
-depth of the wound, its anfractuous conditions, the underminings in 
which the pus collects, the generally bad state of health, the heaviness 
.and the overworked condition of the patient, the want of ventilation 
.and defective hygienic surroundings in which the animal is placed. 
Purulent infection is produced by the ordinary microbes of suppura- 
ition, generally streptococci or staphylococci. The most constant of 
-those, the one that plays the greatest part, is the ordinary (vulgar) 
streptococcus. It acts alone or in concert with staphylococci. It is 
“known that the latter possess various degrees of virulency, and that, 
-alone, they may give rise to pyohemia; but cases of this kind are 
rare. In three cases of purulent infection studied by us from the 
bacteriological point of view, we have twice found streptococci and 
-once associated with staphylococci. 
How do those microbes reach the blood? By what mechanism can 
‘they promote the metastatic abscesses and the other lesions of pyohe- 
mia? ‘The mode of infection, very different in different cases, is often 
-complex. With suppurative phlebitis, infecting emboli may get de- 
‘tached from the intra-venous clot which is infected with pyogenic 
‘microbes, and be carried by the blood into the lungs and other organs. 
‘Within the walls of fistulous tracts, due to and kept up by necrotic 
‘lesions (disease of the withers, of the neck, tendinous quittor), there 
exist phlebitis and lymphangitis from which the infection may start. 
Without phlebitis in old suppurating wounds the granulating surface 
may be torn ; ‘the wound is wounded” in one place; there the tissues 
are no longer protected by their guarding cover, and the blood and 
‘lymphatic vascular canals are open to the agents of suppuration. The 
modifications presented by purulent infection in its mode of expression, 
“its march and gravity, are especially due to the variable virulency of the 
‘microbian species which produce it. 
The propyhlaxis demands the same general precautions as that of 
‘septicemia. It is by the wound that the pyogenic microbes penetrated 
‘into the economy; so that careful attention must be given to the 
‘wound to prevent infection. With wide, deep, irregular wounds, one 
