292 PROTECTIVE INOCULATIONS. 
of ten days a second inoculation of the same kind was made. Six days 
after the second inoculation the fowls (five) and a control hen were 
inoculated with virulent blood from a pigeon, and at the same time fed 
with the chopped-up flesh and liver of a pigeon just dead from fowl 
cholera. The control hen died on the following day from typical 
cholera, the others remained in perfect health. 
CHOLERA. 
The spirillum discovered by Koch in 1884 is now generally recog- 
nized as the specific cause of Asiatic cholera. But recent researches 
indicate that there are numerous pathogenic varieties of this spirillum, 
and show that either an attenuated cholera spirillum or a closely allied 
saprophyte is not infrequently found in the water of rivers in various 
parts of Europe. As this spirillum is found in the intestine of cholera 
patients, and not in the blood, it is evident that its pathogenic action 
depends upon the chemical products developed during its growth, 
and this inference is fully justified by the results of experiments upon 
the lower animals. These chemical products have been studied by 
Brieger, Pfeiffer, Scholl, Gamaleia, Westbrook, and others. 
Brieger (1887) succeeded in isolating several toxic ptomaines from 
cultures of the cholera spirillum, some of which had previously been 
obtained from other sources—cadaverin, putrescin, creatinin, methyl- 
guanidin. In addition tothese he obtained two toxic substances not 
previously known. One of these is a diamine, resembling trimethyl- 
diamine; it gave rise to cramps and muscular tremor in inoculated 
animals. The other poison reduced the frequency of the heart’s 
action and the temperature of the body in the animals subjected to 
experiment. In more recent researches made by Brieger and Frankel 
(1890), a toxalbumin was obtained from cholera cultures which, when 
injected subcutaneously into guinea-pigs, caused their death in two or 
three days, but had no effect upon rabbits. 
Pfeiffer has more recently (1892) published his extended researches 
relating to the cholera poison. He finds that recent aérobic cultures 
of the cholera spirillum contain a specific toxic substance which is. 
fatal to guinea-pigs in extremely small doses. This substance stands 
in close relation to the bacterial cells, and is perhaps an integral part 
of the same. The spirilla may be killed by chloroform, thymol, or 
by desiccation, without apparent injury to the toxic potency of this 
substance. It is destroyed, however, by absolute alcohol, by concen- 
trated solutions of neutral salts, and by the boiling temperature, and 
secondary toxic products are formed which have a similar pathogenic 
