THP] NATURE OF THE AMERICAN SWINE PLAGUE. 357 
field the former have been upon, then the natives begin to die. 
That is about all we know of the nature of Texas fever, ex 
cept the singular assertion that the land-infecting power dies out 
in passing through the organism of but one generation of north¬ 
ern cattle; that is, the infection is not extended by them. That 
question wants better proof. 
Let us consider anthrax for a moment, because it more closely 
resembles the swine plague, and is not so regardful of our north¬ 
ern fields and herds. 
Anthrax is the most acutely malignant of all the known in¬ 
fectious diseases, but fortunately it is so decidedly a fixed disease 
—it requires such peculiar combinations in the climatic and tel¬ 
luric conditions—that there is very little danger of its ever ac¬ 
quiring any such devastating extension over a country as its less 
exacting relatives, in this regard : the swine plague, Asiatic chol¬ 
era, etc. 
Black-leg is another rather exacting member of this group, 
but its demands in this respect differ again from those of anthrax 
and the other infectious diseases. While it requires suitable extra- 
organismal conditions for its support and development, unlike the 
others, it is very exacting about the intra-organismal; it is an 
exclusive and aristocratic black-leg—it selects only the fattest and 
best of the herd, and also selects the young and tender, instead 
of the older members. 
The peculiar danger possessed by anthrax is to be sought in 
the tenacity of life of its germ when in a spore condition. There 
is no known vital object which can exceed these things in their 
resistance to all sorts of changes of temperature and other 
conditions. 
During my visit to Sioux City, la., in July, 1886, to investi¬ 
gate a so-called “ unknown disease,” which proved to be anthrax, 
I took pains to examine the fresh manure from a cow that had 
been exposed for about half an hour to the temperature of the 
air. The rods were developing the dangerous, permanent spores 
in the most beautiful manner and with wonderful rapidity. By 
adding the least amount of water to the manure and placing some 
under the microscope, one could see this process going on better 
