SOME REMARKS ON ANTI-HOG CHOLERA SERUM. 
673 
The characteristics mentioned are perhaps the most promi¬ 
nent ones, but they do not stand alone, and together with many 
others which it would take too much time here to mention, have 
established beyond a dispute the autonomy of the specific micro¬ 
organisms in the pathologic affections under discussion. But 
we would be wrong in concluding, that now the differentiation 
between the latter by means of a bacteriologic examination had 
been made an easy task. The researches of Welch and Clem¬ 
ent * have taught us that very often in hog cholera (intestinal 
form) a secondary pulmonary infection by swine plague bacilli 
supervenes, completing the picture of pneumo-enteritis. 
What is more perplexing still. Smith has demonstrated the 
fact that in the bronchial tubes of normal hogs, there are always 
present certain swine plague-like bacilli of little pathogenic 
power, which under the weakened condition of the organism 
produced by a hog cholera attack, assume a higher virulence, 
entering the lungs and setting up the pulmonary complication. 
This embarrassing multitude of militating factors is made 
more perspicuous by the fact that all of the affections men¬ 
tioned either appear in an acute form or take a more or less 
chronic course. It was indispensable to deal with them here 
shortly in order to show to which degree difficulties surround 
the practical administration of an etiologic therapy. 
Considering the vast losses caused by hog cholera, the promis¬ 
ing task of immunizing or of curing animals by means of such an 
etiologic therapy have been very numerous. Already, in 1886, 
Salmon and Smith succeeded in immunizing smaller animals 
by the administration of germ free culture-fluids, and Schweinitz 
claimed to have achieved the same object by certain substances, 
which he prepared from pure cultures, and which he called 
“ sucholotoxin ” and “ sucholoalbumin.” For the immunization 
of hogs the most diversified methods have been employed, blood 
of diseased animals, dead or attenuated cultures, etc., being used 
as vaccine. But none of these methods have as yet scored a final 
success ; some of them, especially the intravenous injections, had 
* Baumgarten’s Jahresber. 1893, p. 135. 
