202 VETERINARY BACTERIOLOGY 



some cases. Cauliflower-like excrescences of the heart-valves, 

 with consequent valvular insufficiency and embolism, due to the 

 breaking off of these particles, are the characteristic lesions. 



Arthritis. Inflammation of the bone covering (periostitis), 

 infections of the bone-marrow (osteomyelitis), and of the joints 

 (arthritis) are generally the result of streptococcic invasion. 

 In all new-born animals there is danger of infection through the 

 navel, and consequent production of " navel ill " (omphalophlebi- 

 tis). The umbilical vein, according to Moore, becomes heavily 

 infected with bacteria, which invade the joints by metastasis. 

 The selective action of the organisms in infecting certain tissues 

 at one time and others at another is not well understood. Rheu- 

 matic fever in man (acute articular), and probably in animals, 

 has been shown to be sometimes due to Streptococcus pyogenes. 

 The infection atrium in man appears to be the tonsils. 



Suppurative Cellulitis. Under this heading Moore has described 

 the streptococcic infections of the subcutaneous tissues, par- 

 ticularly of the lower extremities. In sheep it is called locally 

 " foot-rot." 



Mastitis. Mastitis is commonly caused by Streptococcus. 

 Here again the particular strain selects a particular organ, and 

 may be transferred from one animal to another by the hands of 

 the milker. Several different species of the Streptococcus have 

 been described as associated with garget or infectious mastitis, 

 but there does not seem to be any good reason for believing them 

 to be anything but specialized strains of the Streptococcus pyogenes. 

 As will be seen later, the presence of Streptococcus in milk does 

 not necessarily predicate mastitis, for non-pathogenic forms are 

 common. 



Immunity. A hemolytic toxin, streptolysin, may be demon- 

 strated in some strains of Streptococcus pyogenes. For this an 

 antitoxin has been produced. It seems probable that there is 

 also a toxin which injures or destroys leukocytes. These toxins 

 vary in amount, however, in cultures of different strains, and seem 

 to vary independently of the virulence. They certainly do not 

 account for the pathogenic nature of the organism. Agglutinins 

 may occasionally be demonstrated, but are not of diagnostic 

 importance. Endotoxins are produced by both virulent and non- 



