154 Br. Klein [May 27, 



matter of the ulcers of the udder is possessed of infective power, 

 inasmuch as on inoculation into the skin of calves the same ulcers 

 are reproduced ; further it was shown that in the ulcers of the cow 

 there existed in large numbers a species of micrococcus which on 

 being j^lanted on artificial nutritive media, such as are used for the 

 study of bacteria, produces in a few days a crop of micrococci, 

 possessed of very distinct characters by which they are distinguish- 

 able from other bacteria. When calves are inoculated from a cultiva- 

 tion of this micrococcus they become after an incubation period 

 affected with a cutaneous and visceral disease the same as the disease 

 of the Hendon cows. To sum up, then, it has been shown that at this 

 Hendon farm there existed certain cows affected with a communicable 

 disease w'hich, in many points of its pathology, bears a great resem- 

 blance to human scarlatina; further, that the milk of these cows 

 gave scarlet fever to human beings ; and, lastly, that a particular 

 microbe was obtained from these cows which in calves produced a 

 similar disease to the disease of those cows. 



In order to complete the evidence thus far obtained, it was neces- 

 sary to prove that scarlet fever in man is due to the presence and 

 multiplication in the blood and tissues of the same micrococcus, and 

 that this microbe, if obtained from human scarlet fever, produces in 

 the cow the same disease as is produced by the micrococcus of the 

 Hendon cows. Now, this proof has been satisfactorily given. In 

 the first place, it has been shown that in the blood and tissues of 

 persons affected with scarlet fever there occurs the same micrococcus 

 as was present in the cow, both being identical in microscopical and 

 in cultural characters. In the second place it was found that the 

 action of this microbe on animals is exactly the same as the micro- 

 coccus found in the Hendon cows. Calves and mice after inocula- 

 tion or feeding with a trace of the growth of both sets of micrococci 

 become affected with cutaneous and visceral disease similar to human 

 scarlet fever ; in calves the disease is of the same mild type as in the 

 Hendon cows. Further it was shown that from the blood and the 

 tissues of these animals infected with one or the other set of cultiva- 

 tions, the same micrococcus was recovered. I will remind you that 

 in all infectious diseases which have been proved definitely to be 

 associated with a particular species of microbes this microbe intro- 

 duced into a susceptible body thrives and multiplies and thus sets up 

 the diseased condition, differing, of course, with the different sj^ecies 

 of microbes. I think I may after this say that this microbe, micro- 

 coccus scarlatinse, is the cause of human scarlet fever ; further that it 

 produces in bovine animals a disease identical with the Hendon 

 disease and human scarlet fever, and that consequently while the cow 

 is susceptible to infection with human scarlet fever, it can in its turn 

 be the source of contagium for the human species, as w'as no doubt 

 the case in that milk e2)idemic from the Hendon farm. 



I shall now give you a striking piece of evidence Avell in harmony 

 with what I have mentioned hitherto. In October 1886, Professor 



