INFECTIOUS MASTITIS Q27 
review of much of the literature on this subject shows that a number 
of cases reported ‘as infectious were isolated or sporadic ones, that is, 
they were in dairies where the disease did not spread to other animals. 
While these may be truly infectious in their nature they should be 
differentiated from the rapidly spreading phlegmons which are easily 
recognized as infectious (contagious) mastitis. 
If we take into account the variety of anatomical changes which 
have been described in the various udder affections, we can reason- 
ably admit that different agencies may have been instrumental in 
their production. The various species of bacteria which have been 
isolated from the udder lesions may very likely have been of etiological 
importance in their respective cases. Bang, Hess, Kitt, Lucet 
and Nocard have pointed out that infectious mastitis is caused by 
bacteria which gain access to the udder through (1) the milk duct, 
(2) the blood circulation and (3) the lymphatic system. 
Already the facts have been pointed out, that the udder is normally 
more or less extensively invaded with bacteria and that certain 
species seem to persist in the milk ducts of the glands when once 
they become localized there. If these results apply to cows generally 
as rigidly as they did to those examined, an explanation for the 
presence of a variety of bacteria in the affected udders is not difficult 
to find. Whether these particular organisms, under certain condi- 
tions, would become primarily responsible for udder disease is not 
known. The evidence suggests that a number of bacteria, hereto- 
fore described as the cause of mammitis, were in the affected glands 
by virtue of their presence in the normal udder. Concerning these 
points the results of additional investigations are much needed.* 
*The writer has examined the milk secretions from the affected cows in two quite 
serious outbreaks of mastitis. In the first, the milk was drawn in sterile bottles 
after the udders and the hands of the milker had been thoroughly washed in a 1 to 1000 
solution of corrosive sublimate. In all, there were eight samples of milk taken from 
as many different cows. In six of the eight specimens streptococci appeared in pure 
culture. In the other two cases micrococci were associated with the streptococcus. 
In the second outbreak, the milk from four diseased, udders was drawn with aseptic 
precautions directly into tubes containing slant agar and promptly sent to the labora- 
tory, where it was carefully examined. From two cases pure cultures of streptococci 
were obtained, while those from the others were impure. The streptococci obtained 
from the twelve cases appeared to be identical and the clinical aspect. of the disease 
in the different animals was‘the same. 
In a dairy that was under close observation by Ward, one cow was found to be 
troubled in one quarter of the udder with an inflammatory process which produced 
thickened masses in the blood-stained milk. From this milk a streptococcus was 
isolated in pure culture. It could not be differentiated from the one isolated from 
the cows in the outbreaks mentioned. Another cow in this herd was found to have 
her udder permanently infected with a streptococcus. Another animal in the same 
dairy suffered repeatedly from acute streptococcus mastitis. 
