A BACTERIOLOGICAL STUDY OF EQUINE FISTULAS. 
345 
The extent of the changes in the tissue depends on the condi¬ 
tion of the tissue and the virulence of the pus-organism. The 
tissues, in their endeavor to limit the action of the irritant, 
always produce the same exudation, but the change this under¬ 
goes under the influence of different irritants, and under different 
conditions, naturally differs and gives rise to different diseases. 
Suppuration is a complication due to the action of certain 
micro-organisms. Most of the pathogenic bacteria under ordi¬ 
nary circumstances do not reproduce themselves outside the 
body, but their resistance to heat and cold, moisture and dry¬ 
ness, is so great that they retain their disease-producing quali¬ 
ties often for an indefinite period of time, and after their 
entrance into the body, meeting with a proper nutrient medium, 
they exert their specinc pathogenic effects. 
We have now taken into account the complex anatomy of 
the parts, the large congregated mass of muscular and cellular 
tissue with broad tough sheets of fascia lying between, making 
the most favorable place for the action of the microbes and the 
formation of pus. We have also studied the action and effect 
of the micro-organisms on the tissue. 
We may now consider the susceptibility of the parts to the 
action of the pus-organisms; also the action of the organisms 
on those parts. 
The respective location of these parts on the animal makes 
the blood circulate slowly, therefore making the capillaries and 
small blood-vessels very liable to become plugged with the or- 
ganisms, causing stasis and the result usually following it. 
The large amount of loose cellular tissue in these parts also 
makes them more susceptible to the action of the organisms. 
The action or result of the organisms are to set up a point of 
irritation, causing inflammation and breaking down of the tissues 
into pus cells by the ptomaines which they produce. 
September i, 1893. Case No. 1.—The animal was six years 
old and had been used for general work. It presented a con- 
siceiable swelling on the right side, extending far back on the 
withers. The case had no history of injury to the parts, but 
