118 ABSTRACTS 



epidemic sore throat are virulent streptococci of human origin. There 

 is still some difference of opinion, however, as to the virulence of these 

 human types of streptococci for the cow. Davis and Capps^ have 

 reported experiments in which they were able to produce mastitis in 

 cows by the injection of hemolytic streptococci of human origin into 

 the udder, and they have demonstrated conclusively that mastitis 

 may exist in a cow's udder without any physical signs being present 

 other than the invading bacteria and an increased number of leukocytes 

 in the milk. Smith and Brown^ are inclined to believe from their 

 studies that the streptococci commonly associated with bovine mastitis 

 are different from those found in epidemic sore throat and do not 

 cause human throat infections. Moreover they infer that organisms 

 of human origin do not cause bovine mastitis but may grow and multi- 

 ply in the milk ducts, a condition which might explain outbreaks of 

 tonsillitis. During the past year an experimental stud}^ has been made 

 of the comparative virulence of human and bovine types of streptococci 

 for the cow, along with observations as to the behavior of these organ- 

 isms over long periods of time in the cow's udder and the following 

 results have been obtained. 



In six instances mastitis has been produced in normal milch cows 

 by the injections of small amounts of streptococcus cultures into the 

 milk ducts. Streptococci derived both from human and bovine 

 sources were used in these experiments. It was found that hemolytic 

 streptococci with all the characteristics of the human type may be 

 highly virulent for cows when injected into the milk ducts. They 

 produce a severe mastitis which may result in an atrophy of the mam- 

 mary gland. It was also observed that organisms of this type 

 may grow and multiply in the milk ducts without causing any visible 

 changes in the udder, but the milk in this instance contained an in- 

 creased number of leukocytes and streptococci. Hemolytic strepto- 

 cocci from milk and the Streptococcus lacticus may produce an acute 

 inflammation of the milk ducts but this change in my experience was 

 of a transitory nature and the mammary gland regained its normal 

 function very rapidly. In these observations streptococci derived 

 from human sources proved to be more virulent for the cow than the 

 milk strains. 



In three instances of bovine mastitis all of which were due to hemo- 

 lytic streptococci of the human type, there were no noteworthy changes 

 in the morphology or cultural characteristics of the invading organisms 

 observed in frequent examinations of the milk throughout the course 

 of the infections. The distinguishing characters primarily noted for 

 each organism are still present, and there are no modifications which 

 might be considered as indicating a change from one type to another. 

 These infections are still active 304, 272 and 234 days respectively 

 after the udders were injected. Also there were no noteworthy changes 



' Jour. Infec. Dis., 1914, xv, 135. 

 ^ Jour. Med. Res., 1915, xxxi, 455. 

 * Mathers, G., Jour. Inf. Dis., 191G. 



