Etiology. Pathogenesis. Anatomical Changes. 599 



favorable circumstances, suck as feeding on maize, bran, beets 

 or potatoes, after overexertion, faulty attention, the presence 

 of parasites, assume pathogenic properties. The diseased 

 horses can infect others, because the streptococci which have 

 become pathogenic are passed out with the feces and urine, 

 and should these come into contact with food or water 

 or be introduced into healthy horses in any other way, infection 

 results. By feeding a horse, a donkey and a male goat on some 

 suspected hay Zwick succeeded in causing the typical dis- 

 ease, although under natural circumstances the disease ap- 

 pears to be confined to the horse. Comeny and Sorriau are in- 

 clined to think that infection takes place by way of the urethra 

 and the urinary tract. On the other hand, Kull and Duvinage 

 observed the disease in connection wdth an infectious catarrh of 

 the upper air passages. 



Pathogenesis. From the experiments that have been made 

 up to the present the only conclusions that can be drawn are 

 that the streptococcus causes a general infection, associated 

 with hemorrhages and parenchymatous degeneration of various 

 organs. No proof has been furnished as to the inflammatory 

 nature of the lesions in the bone marrow and the central ner- 

 vous system. Similar extravasations occur in any case in which 

 there is dissolution of the blood. An explanation is necessary 

 as to what extent the symptoms of paralysis are due to the 

 hemorrhages in the spinal cord on the one hand, or to the lesions 

 in the long bones and the resulting pain on the other, or whether 

 they may be caused by the septicemic infection. 



Anatomical Changes. The peritoneum shows petechial 

 hemorrhages. The mesenteric glands are markedly swollen 

 and infiltrated with blood-stained serum. The spleen is normal 

 or it may be enlarged three or four times. The liver and kid- 

 neys are enlarged and show parench5^natous degeneration and 

 hemorrhages. The bladder often contains urine stained with 

 blood, the mucous membrane is beset with hemorrhages and 

 the wall somewhat thickened. In a numl)er of cases the con- 

 nective tissue around the bladder and genital organs is gelati- 

 nous and there may be edematous swelling of the lips of the 

 vulva or of the sheath, and sometimes of the skin of the peri- 

 neum. The mucous membrane of the vagina is in such cases 

 studded vritli small hemorrhages. The marrow of the long and 

 flat bones is stained brown or brownish-red, either diffusely or 

 in patches, owing to hemorrhages, the appearance resembling 

 that seen in infectious anemia (see Vol. I). There is a blood- 

 stained fluid in the epidural and subdural spaces, the arachnoid 

 and the pia mater are swollen and gelatinous, and the latter 

 appears to l)e beset w^ith small hemorrhages. In the spinal cord 

 there are numerous minute hemorrhages and reddish-yellow 

 softened centers, especially around the central canal, which w^ill 



