44 



Blackleg. 



isolated cases of the disease, but it is still a matter of con- 

 tention whetlier the disease appears in horses or not. 



Aocordiug to a compilation by Tillmann, out of 614 animals suffering from 

 blackleg, 7 were from 1 to 4 weeks old, 23 from 2 to 3 months, 94 from 3 to 6 

 months, 449 from y^ to 4 years, and, finally, 41 were above 4 years old. 



Symptoms similar to those of blackleg, and analogous anatomical 

 changes may also be produced by other bacteria (the so-called psexido- 

 blackleg bacilli). Thus Kerry has isolated a bacillus from a guinea 

 pig which had been inoculated with blood from a cow supposed to 

 have died from blackleg. This bacillus grows at a higher tem- 

 perature than the blackleg bacillus, produces no spores, and is patho- 

 genic not only for guinea pigs, but also for rabbits (bae. edematis 

 •thermophilus). Preisz found in one case, which otherwise was similar 

 to blackleg in every way, a considerably longer and thicker bacillus 

 than in common blackleg. 



Lignieres and Bidart in their clinical reports on diseases similar 

 to blackleg in Argentine refer to an affection which is known under 

 the name of Mancha (=spot, owing to the dark color of the skin over 

 the edema). Calves from 6 to 10 months old contract the 

 disease exclusively and succumb within 24 to 28 hours. The 

 disease is caused by a bacillus similar to the blackleg bacillus, 

 but it is pathogenic for young rabbits, horses, and pigeons. 

 Protective vaccination with blackleg virus is without effect. 



Pathogenesis. Toxin-free spores which have 

 penetrated into normal healthy tissues are soon taken 

 up by phagocytes and digested; if, however, at the 

 same time, other bacteria or grains of dust have 

 gathered, and the tissue, particularly the muscula- 

 ture, is not quite sound, or if, at the involved place 

 an extravasation of blood exists, then the spores, 

 protected against the phagocytes, begin to germinate, 

 and the bacilli thus created continue to multiply 

 through fission. Under natural conditions a small 

 disturbance in the tissue, a strain of the muscles or a 

 hemorrhage (blow by a stick or a horn), may cause 

 the bacteria which have reached the blood from the 

 intestines, and'otherwise are soon destroyed, to locate 

 at these points, to increase in number, and excite the 

 pathological process. 



Where the bacilli appear in abundance, a serous 

 inflammation and sometimes also small hemorrhages 

 sSb cui- '^^^^ ^® observed. Under the influence of the toxins, 

 ture of the the musculature degenerates, and, through the de- 

 Biackieg gtructiou of the nitrogenous matter, gases are 

 gr'ape sugar formed. The toxins are also absorbed by the body 

 agar. fluids and cause the general symptoms accompanying 



the local process ; they also reduce the power of resistance of the 

 tissues against the pathogenic effect of the virus (Eoger). 



According to the investigations of Leclainche & Vallee, cultures 

 containing spores and heated from 80 to 85 °C. are inactive, as the 



