Pathogenesis. Anatomical Changes. 45 



spores in the tissues are digested by the phagocytes within 48 hours. 

 These spore-containing cultures cause the disease, however, if active 

 toxin is added or if they are injected mixed with sand or saprophytic 

 bacteria (bac. prodigiosus, proteus vulgaris, staphylococcus albus). 

 The spores will also show a greater pathogenic activity by the addi- 

 tion of a small amount of 20^0 lactic acid, salt solution or diluted 

 alcohol, and also through a traumatic injury immediately before or 

 after the infection. These saprophytic bacteria, the sand and the dead 

 tissue protect the spores mechanically against the phagocytes and make 

 their development possible. The same result is produced by the chem- 

 ical substances as well as by the inoculation of toxins contained in 

 unheated cultures, through negative chemotaxis. 



Anatomical Changes. Characteristic of blackleg is the 

 crepitant swelling occurring anywhere on the rump or extremi- 

 ties, more or less distinctly circumscribed, above which the skm 

 appears sound, or in rare cases, partly necrotic, and therefore, 

 stiff, parchment-like, and dark colored. The subcutaneous tissue 

 is red or infiltrated with a yellowish, gelatinous exudate, at 

 places intermixed with hemorrhages and gas vesicles, and m the 

 deeper parts similarly changed connective tissue separates the 

 single muscle fibres from each other. The musculature of the 

 swollen part is dirty brown or dark red ; at the periphery^ it 

 is darker red or dull yellow with black stripes, and either in- 

 tersected with bloody "serous liquid or is spongy and dry (the 

 latter with great development of gas). The dirty red, or claret 

 colored liquid squeezed from the swellings contains gas bubbles 

 in abundance which give off an odor suggesting rancid butter. 

 In the tissue surrounding the swelling the lymph vessels are 

 sometimes distended, filled with lymph and gas, ^\^iile the 

 lymphatic glands are acutely swollen, edematously infiltrated, 

 and sometimes intermixed Avith hemorrhages. 



Crepitant swellings appear in rare cases in the musculature 

 of the tongue, throat, and diaphragm, from which points they 

 may also involve the muscles of the shoulder and arm (Hen- 

 ninger). They may likewise be found in the loin or m the 

 muscles between the ribs. _ 



The internal organs show few conspicuous lesions and no 

 constant changes. Relatively often a reddish serous liquid is 

 found in varying amounts in the thoracic cavity. Further, there 

 may be present on the pleura, as well as on the epicardium, a 

 reddish gray fibrinous exudate sometimes mixed with dirty red, 

 jelly-like substances, or the parietal pleura may be covered 

 witii soft, jelly-like, wine-colored deposits (Foth, Katona, iill- 

 mann). In the lungs, the interlobular septa may be infiltrated, 

 and the lobules themselves edematous. In very rare cases the 

 heart muscle at localized points is dark red and edematous 

 (Tillmann) or necrotic (Blome), and the epicardium is covered 

 with strips or tufts of exudate. -, t . 



In the abdominal cavity lesions are frequently found wliicli 

 are similar to those in the thoracic cavity. The spleen is gen- 



