INFECTIOUS DISEASES OF CATTLE. 465 



inhaled by workmen in establishments in which wool, hides, and rags 

 are worked over, and it is therefore known as wool-sorter's disease. 

 In the latter case the disease is contracted by eating the flesh of dis- 

 eased animals which has not been thoroughly cooked. These forms 

 of the disease are more fatal than those in which the disease starts 

 from the skin. 



bl.acklj;g.^ 



Blackleg, bla^kquarter, quarter-ill. symptomatic anthrax, chxtrhon 

 symptOTnatique of the French. Rauschhrand of the Germans, is a 

 rapidly fatal infectious disease of young cattle, associated with exter- 

 nal swellings which emit a crackling sound when handled. This dis- 

 ease was formerly i*egarded identical with anthrax, but invCvStigations 

 carried out by various scientists in recent times have definitely proved 

 the entire dissimilarity of the two affections, both from a clinical and 

 causal standpoint. The disease is produced by a specific bacillus, 

 readily distinguishable from that causing anthrax. (PI. XXIX, 

 fig. 4.) Cattle between 6 months and 2 years of age arc the most 

 susceptible. Sucking calves under G months are rarely attacked, nor 

 are they as susceptible to inoculation as older animals. Cattle over 2 

 years of age may become affected, but such cases are infrequent. 

 Sheep and goats may also contract the disease, but man. horses, hogs, 

 dogs, cats, and fowls appear to be immune. 



Like anthrax, blackleg is more or less restricted to definite locali- 

 ties. There are certain pastures upon which the disease regularly 

 appears in the summer and fall of the year. As to any peculiarities 

 of the soil nothing is definitely known. Some authors are inclined 

 to regard moist:, undrained, and swampy pastures favorable to this 

 disease, but these theories will hardly hold, as it is found in all kinds 

 of soils, in all altitudes, at all seasons of the year, and under various 

 climatic conditions. It occui-s in this country from the Atlantic to 

 the Pacific and from Mexico to Canada, but it is more prevalent in 

 the Western and Southwestern States. In Europe it exists in France, 

 various parts of Germany, in Belgium, Norway, Denmark, Italy, and 

 in the Alps of Switzerland. In Africa it occurs in Algeria and to 

 some extent in Natal and bordering countries. In South America it 

 prevails quite extensively throughout Argentina. Cattle in Cuba 

 and Australia also suffer. 



The cause of the disease is a bacillus resembling in some minor 

 respects the anthrax bacillus and differing but little from it in size. 

 It also possesses the power of forming within itself a spore. In 

 Plate XXIX. figure 4. this is represented as an uncolored spot located 

 in one end of the rod, which is enlarged so that the rod itself appears 

 more or less club-shaped. AAHiat has already been stated concerning 



' For detailed information regarding blackleg and the free distribution of blackleg 

 vaccine, write to this department for Bureau of -\iiimal Industry Circulars Nos. 23 and 31. 

 16923°— 12 30 



