20 Veterinary Medicine. 



of even a potent microbe alone. Some of the worst cases follow 

 on a wound, the seat of complex infection, and even saprophytes 

 are to be dreaded in this connection. This may operate in vari- 

 ous ways, either by mutual combinations or decompositions of 

 the toxic products of associated germs producing more deleterious 

 products, or by the individual action of one ptomaine or toxin on 

 leucocytes, haematoblasts, sera, or tissue, laying it more open to 

 the attacks of those of' another microbe which by itself would 

 have been comparatively harmless. 



Koch's experiments showed that the attack is violent in ratio 

 with the size of the dose : one thousandth part of a drop of pysemic 

 blood was harmless to the rabbit, while one tenth of a drop killed 

 in one hundred and twenty- five hours, and a syringe full in forty 

 hours. 



In ordinary cases of pysemia the occurence of internal /A/i^dzVw 

 or arteritis with the inevitable thrombosis is an important step in 

 causation. Any inflammation of the inner coat of the vessel leads 

 promptly to the formation of a coagulation of the 'contained blood, 

 and blocking of the lumen. Beginning on the diseased or 

 abraded surface, the clot forms backward along the line from 

 which the blood normally comes (proximal in the arteries ; distal, 

 in the veins), until it reaches the next considerable colateral 

 branch. The clot is firmly adherent to the intima except at the 

 free end, which is conical and projects into the blood current. 



If small portions are detached from the thrombus and washed 

 on in the blood stream they become arrested when they reach a 

 vessel too small to admit them, it may be a smaller artery, or it 

 may be a capillary, and always in the line of the circulation, — 

 from the systemic circulation to the lungs, or from the lungs to 

 the system at large. This is embolism. Wherever arrested, the 

 contact of the leucocytes and hsematoblasts with the inner coat 

 of the vessel, leads to metabolic changes and firm adhesion, and 

 the pus microbes in the clot determine suppuration and abscess. 



Eberth and Schimmelbusch have shown that the haematoblasts, 

 even more than the other blood elements, when acted on by the 

 pus microbes become viscous and stick not only to each other, 

 but to any floating body, and to the inner serous coat of the 

 vessel, particularly when the latter has been abraded or injured. 

 This clumping together of the hsematoblasts forms white clots 

 which block the smaller vessels, but in the viscous condition they 



