240 SCIENCE FROM AN EASY CHAIR 



spiral thread in the blood this!) the recurrent fever of 

 East Europe each producing its own special poison or 

 other chemical substance. 



So it went on till Koch, of Berlin, discovered the 

 bacillus of tubercle and Hansen that of leprosy. 

 Others had failed to find what Koch now found as the 

 result of a special mission on behalf of the German 

 Imperial Government to India (undertaken as nearly as 

 I can recollect about the year 1884) namely, the living 

 organism (Fig. 46) which by its growth in man's intestine 

 causes Indian cholera. Koch found a spiral threadlike 

 " bacterium " in cholera patients, which readily breaks up 

 into little curved segments like a comma (each less than 

 the one ten-thousandth of an inch in length), and swarms 

 by the million in the intestines of such patients. He 

 showed that it can be cultivated in dilute gelatinised broth, 

 and obtained in spoonfuls. It was, however, only with 

 great difficulty that he could produce cholera in animals 

 by administering this pure concentrated growth of cholera 

 germs to them. 



Then a most courageous thing was done. A great 

 and very acute investigator of cholera in Munich, Petten- 

 kofer by name who did not believe that Koch's 

 comma-bacillus was really the effective germ of cholera 

 himself swallowed a whole spoonful many millions 

 of the cultivated cholera germ. His assistants did the 

 same and none of them suffered any ill effect ! Few, if 

 any, of the investigators of this question gave up, as a 

 consequence, their conviction that Koch's bacillus was 

 the real and active cause of cholera. They supposed 

 that it must be necessary for the human intestine to be 

 in a favourable condition an unhealthy condition for 

 the Koch's bacillus to multiply in it. It was by this time 

 known that bacteria of all kinds are exceedingly sensitive 

 in regard to the acidity or alkalinity, the oxygenation or 



