REMARKS ON PATHOGENIC BACTERIA. 239 
Another illustration is afforded by the Southern, Spanish, or so- 
called Texas cattle fever, which, undoubtedly, is a_bacteritic 
disease. The pathogenic principle (the bacteria) which seems to 
develop on the grasses of the South, and is probably taken up by 
the cattle with drinking stagnant water, or by eating semi-decom- 
posed grasses, does not visibly affect the native cattle, while, on 
the other hand, cattle imported from the North will take sick, and 
almost invariably (at least in a majority of cases) will die within a 
short time, often within a few weeks. But the native southern 
cattle, if taken from their native range and driven North at the end 
of the winter, after the spring rains and warmer weather have set 
in, or, in other words, after the old grass of last year’s growth has 
commenced to decompose, and after new, young grass has made 
‘its appearance, will spread death and destruction wherever they go, 
while they themselves will remain healthy, or at least do not 
become affected with southern cattle fever. These southern cattle 
seem to carry and to propagate the pathogenic bacteria of the 
southern fever in their saliva. At any rate, if northern cattle 
graze where the grass has been contaminated with the slaver or 
saliva of such southern cattle, or if they (the northern cattle) drink 
water from ponds or water-holes, etc., which have been polluted 
with the slaver of southern cattle, the disease (southern cattle 
fever) is sure to make its appearance, and to become very 
destructive among the northern cattle after a period of incubation 
varying from three to thirteen weeks. But these northern cattle, 
even if suffering from the fever, are not able to infect other cattle 
that may come in contact with them, occupy the same pastures, or 
frequent the same watering places. To put it in a nutshell: cattle 
that take the disease do not communicate it, either directly or 
indirectly, and cattle that communicate it do not take it. Further, 
as already stated, southern cattle, as long as they occupy their 
native range, possess immunity. But this immunity disappears if 
the southern cattle are taken a certain distance further south, for 
instance from Northern Texas or the Indian Territory to Southern 
Texas, or from Southern Texas to Cuba, or other parts of the West 
Indies ; again, if southern cattle are taken North, and are kept 
there one winter, because in that case their susceptibility or predis- 
position will become just the same as that of native northern cattle. 
These clinical facts, not only observed by myself, but also by a 
great many others, go far to show that the bacteria of southern 
cattle fever require, in order to become malignant (pathogenic) 
certain conditions, which are not existing, or perhaps have become 
exhausted in the southern cattle while on their native range, but 
are again reproduced if these same cattle are wintered, even if 
only one winter, further north, for instance, north of the Indian 
Territory. Also, that further south, for instance, in Cuba, much 
