208 APPLIED BACTBRIOLOGVr 



specimens. The Dunham solution tubes are incubated for 

 twelve hours only, and are then probably cloudy from the 

 rapid growth of the organisms, and the production of indol 

 and nitrites has proceeded sufficiently far to cause the 

 appearance of the indol reactions (a distinct rose-madder 

 tint) on the addition of a drop of pure sulphuric acid. 



Many other organisms besides Koch's ' comma ' also 

 produce indol and nitrites in sufficient quantities to yield 

 the indol reaction, but not in this time (twelve hours), so 

 that if the indol reaction is obtained, and the organisms are 

 microscopically similar to Koch's ' comma,' we may report 

 positively without delay. It is always advisable to adopt 

 this method of inoculation into Dunham solution, because 

 not only do we get the indol reaction, but a plentiful crop 

 of organisms, probably nearly a pure culture, on which to 

 do further work. In cases of true cholera the organism 

 irequently cannot be demonstrated in the stool when the 

 patient is on the way to recovery, so that the inability to 

 demonstrate the organism in cases three or four days from 

 commencement of the attack must not be taken as evidence 

 that the disease was not true cholera. 



In the diagnosis of cholera the most valuable information 

 is afibrded by the intraperitoneal injection of guinea-pigs 

 with pure cultures. It must be noted that the lower 

 animals do not suffer from the disease under natural con- 

 ditions, but symptoms simulating human cholera infection 

 have been produced in animals as the result of the inter- 

 ference of the stomachic and intestinal processes by the 

 administration of alkalies, opium, etc. The most prominent 

 symptoms in the intraperitoneal injection into guinea-pigs 

 are subnormal temperature, distension of the stomach, and 

 ultimately profound collapse. The peritoneal effusion may 

 be clear, or may be somewhat turbid, due to its containing 

 flakes of lymph. The organisms are practically confined to 



