MICRO-ORGANISMS AS PARASITES. 23 



they easily accommodate themselves to extremes of temperature, 

 and are with difficulty killed by either heat or cold ; they are 

 peculiarly sensitive to other influences. They will not grow 

 without air or in an atmosphere of carbonic acid, but they are not 

 destroyed. But one thing is fatal to comma bacilli, and that is to 

 be dried. This peculiarity was found out accidentally. Droplets 

 of meat-infusion containing comma bacilli had been placed on 

 cover-glasses, and allowed to dry. On being examined, no growth 

 was found upon any cover-glass ; all the germs were dead. This 

 was the more surprising to Koch, because the bacillus of anthrax, 

 which in many respects resembles that of cholera, can be dried 

 with impunit)'. To be dried for two hours is fatal to most, and 

 for three hours is fatal to all cholera bacilli. 



Their constitutional peculiarities also give a clue to the reason 

 of the recovery of cholera patients, even from the stage of 

 collapse. The bacilli grow with extraordinary rapidity; cultivated 

 with other bacteria they quickly outgrow them, and this rapid 

 growth lasts for about twenty-four hours. But in two, or at the 

 most three days, the comma bacilli die, and the other bacteria which 

 may be present survive them. If the patient, therefore, can survive 

 his internal enemies, he has a chance of recovery. This life- 

 history forms a strong contrast to that of the bacillus of leprosy, 

 which can live and ceaselessly multiply for eight or ten years, and 

 dies — if even then it dies, only with its human victim. The use 

 of disinfectants has also been placed on a scientific basis by the 

 study of the individual constitutions of micro-organisms. The 

 cholera bacillus, for instance, will not develop in infusions 

 containing alcohol, lo per cent. ; camphor, i part in 300 ; 

 carbolic acid, i part in 400 ; quinine, i part in 5,000 ; and 

 corrosive sublimate, i part in 100,000. 



The inhibitory action of quinine upon micro-organisms gives 

 us a clue to the reason of its action as a specific in fevers. And 

 before leaving this subject, I should like to refer my readers to a 

 profoundly interesting paper on the action of quinine on the 

 hematozoa of malarial fever, by Dr. Osier, of the University of 

 Pennsylvania, which appeared in the British Medical Journal for 

 March, 1887. 



I will now return to the comma bacillus, and the question of its 



