BOVINE MAMMITIS 613 



Gelatin. Schiitz and Poels failed to grow the organism in stroke culture : 

 Sand and Jensen succeeded in obtaining cultures both on the surface and in 

 stab culture, but the former were very scanty indeed. 



With the strain mentioned above Besson secured a distinct growth on the surface 

 of gelatin at 22 C. ; the colonies were discrete and transparent, and numbered 

 about ten. A sub-culture sown on gelatin on the eighth day failed to grow. 



Potato. No apparent growth takes place on this medium. 



Serum. On sloped serum the growth is fairly abundant. Small, semi- 

 transparent, lenticular colonies at first appear ; these soon become confluent 

 and form a rather thick, grey, iridescent layer. The streptococci often show 

 a very distinct capsule on microscopical examination. 



Milk. The streptococcus coagulates milk in 6-8 days. 



SECTION III. BIOLOGICAL PROPERTIES. 



Viability. The streptococcus of strangles is a very delicate organism. 



Besson found that a very actively growing culture in broth was dead in 12 days. 

 When sown from agar on to agar or from gelatin on to gelatin, sub-cultures almost 

 always fail. With an organism which grew well when first sown on agar from 

 broth, Besson obtained a scanty growth on the second sub-culture on agar but prac- 

 tically none on the third. 



Immunity. The immunity resulting from an attack of the naturally 

 acquired disease is of very short duration. Sand and Jensen succeeded in 

 immunizing a horse by inoculating it intra-venously with a virulent culture 

 and the animal subsequently proved to be immune to intra-nasal in- 

 oculation. 



The antistreptococcal serum of Aronson has proved effective as a prophy- 

 lactic in experiments with the streptococcus of Schiitz, provided that the 

 latter had undergone several passages through mice : it is however totally 

 ineffective in the case of an organism obtained direct from the horse (Aronson). 



II. Streptococcus mammitis bovis. 



(Contagious mammitis of coius.} 



Contagious mammitis of milch cows is due to an infection with streptococci 

 (Nocard and Mollereau) : the organism may be found in very large numbers 

 in the milk of the affected beasts. 



The disease is characterized by the formation in the gland of an indurated nodule, 

 which may attain the size of the fist and even invade the whole organ. The disease 

 runs a chronic course and does not endanger the life of the animal : it is spread 

 by the conveyance of the specific organism from one cow to another on the hands 

 of the milker. 



The milk shows the following characteristic changes. Microscopically it is seen 

 to contain pus cells and numerous chains of cocci. The reaction is occasionally acid. 

 Sometimes the milk is normal in appearance at the time of milking, but it rapidly 

 turns acid and coagulates. If collected aseptically in sterile tubes (p. 201) and 

 kept at room temperature the milk soon turns acid and clots while the streptococci 

 increase in number. 



SECTION I. EXPERIMENTAL INOCULATION. 



The inoculation of a few drops of a young culture or of some infected milk 

 into the teats of cows or goats produces a mammitis with all the features of 

 the spontaneous disease. Laboratory animals are not susceptible. 



