16 MASTITIS OF THE COW 



The local blood-infection, which is of importance to the 

 udder, is through infection of the blood of the aorta. 



Causes. — A blood-infection can be produced in differ- 

 ent ways. Infectious material may be picked up by the 

 leucocytes in an infected area in the intestines or in other 

 organs rich in bacteria and be carried by them into the blood 

 stream. In a wound infectious organisms can grow di- 

 rectly in ruptured vessels. In the infection of an organ the 

 primary lesion (necrosis) may become permeated with in- 

 fectious organisms, which surround the vessels of the pri- 

 mary lesion, inducing deep necrosis, so that a blood-infec- 

 tion may take place through the walls of these vessels. 

 Blood-infection can be induced through infectious ulcera- 

 tion of a vessel wall. Should the lymph become infected 

 (lymph-infection) this fluid can finally infect the blood. 



The usual causes of infection of the blood of the aorta 

 is a lung-infection or an infectious endocarditis. 



If the blood of other organs, for instance of a wound or 

 of a uterus, as in infectious metritis, be infected the blood 

 of the aorta can still remain sterile, since the infectious 

 material is filtered out in the lungs. This is the rule for 

 infectious organisms of positive chemotaxic action, while 

 on the contrary infectious organisms of negative chemo- 

 taxic action easily pass through the lungs. 



With infectious pneumonia usually a blood-infection 

 is brought about through ulceration of a vein wall with 

 emptying of infectious fluid material into the blood of 

 the veins. 



The exudate discharges itself into the vein gradually 

 and thus divides itself minutely. It becomes further com- 

 minuted in its passage in the vessel by impact against the 

 vessel wall, and through the action of the current eddies in 

 the vessel ramifications. A drop of exudate discharged 

 into the vein can become so finely divided in this way that 

 it can be distributed over an incredibly large area. 



