498 
has led to a number of investigations. Injections of milk or cultures 
isolated from milk into the tissues and peritoneal cavities of animals 
gave varying results. In some cases death of the animal ensued. It 
was found that as a rule when the organisms were pathogenic this 
property was gradually lost by cultivation on artificial media, and 
could be increased by carrying through a series of animals. Heine- 
mann® in a recent study succeeded in raising the virulence of a number 
of strains of Streptococcus lacticus, by passage through successive rab- 
bits, from almost nil to an equality with that of the Streptococcus 
pyogenes. Unfortunately the virulence for animals is not a certain 
index of the virulence for man. 
Attempts to distinguish S. lacticus and S. pyogenes by hemolytic 
and agglutinative tests have been made by Schottmuller, * 6 Lubenon, c 
Schlesinger/ and Muller 6 and Bergey (loc. cit.). No constant 
results have been obtained. Muller found that milk streptococci 
were almost as often hemolytic as the S. pyogenes , and heterologous 
strains were more strongly agglutinative than homologous. As has 
been pointed out, no specific characters have been revealed by cul- 
tivation on various media. 
In view of the facts presented the assumption seems justified 
that the Streptococcus pyogenes and the Streptococcus lacticus , the 
common organism of lactic-acid fermentation, are indistinguishable 
by our present methods. 
Briefly, the conclusions which present themselves are as follows: 
(1) Many leucocytes and streptococci are present in the normal 
milk of a healthy cow. 
(2) Leucocytes and streptococci are as a rule more numerous in 
the milk of diseased than in that of healthy cows. 
(3) As an aid to veterinary inspection the number of leucocytes 
may furnish some information of value. If a dairy milk shows an 
unusually high leucocyte count, a special examination of the herd 
for garget, etc., should be made. 
(4) No satisfactory method has been devised for distinguishing 
the pathogenic from the nonpathogenic streptococci in milk. Their 
significance is therefore a matter for further study. 
(5) In view of the recent researches upon Streptococcus lacticus no 
constant relationship may be expected between the number of strep- 
tococci and the number of leucocytes in milk. 
a Journ. of Infect. Diseases, vol. 4, No. 1, 1907, p. 89. 
& Munch. Med. Woch., 1903, Nr. 50, S. 909. 
c Centralbl. f. Bakt., 1902. 
d Zeitschr. f. Hyg., Bd. XLIV, 1903. 
« Archiv. f. Hyg., 1906, Bd. 56, S. 90. 
