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 to these 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 aerobic 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 



