210 APPLIED BACTERIOLOGY 



line, the indol reaction became less and less marked, and 

 the organism liquefied gelatine more slowly ; but on trans- 

 ferring them to ordinary peptone salt solution, the indol 

 reaction was again obtained in a few hours. 



SanareUi {Zeitsch. f. Hygiene, vol. xi.) has recently 

 isolated no less than thirty-two vibrios from water, morpho- 

 logically distinct from each other, all of which gave a 

 distinct indol reaction. Four of these organisms he found 

 to be extremely pathogenic to animals, producing symptoms 

 in guinea-pigs undistinguishable from those given by the 

 true cholera spirillum. SanareUi is of opinion that many 

 varieties of spirilla may exist in water capable of producing 

 a disease in man and animals practically identical with 

 true cholera, and that the assumption hitherto held that 

 this disease is produced by only one particular variety of 

 vibrio must be abandoned. 



Occurrence and Distribution. — -The disease is endemic in 

 many parts of India, particularly the Delta of the Ganges ; 

 in countries in which it is not endemic its course may be 

 traced along the ordinary lines of traffic, showing that it is 

 imported by travellers. The recently-issued report of the 

 Medical Officer of the Local Government Board (' Cholera 

 in England,' 1893) shows how perfectly the disease may be 

 excluded from a country by the careful execution of strin- 

 gent regulations to prevent the landing of persons suffering 

 from the disease, or coming from infected ports without 

 undergoing due quarantine and disinfection. The season 

 of the year has great influence on the spread of cholera, 

 and if infection does not reach us till the cold weather is 

 about to set in, it is improbable that very much harm will 

 be done, though isolated sporadic cases may occur during 

 winter. 



Cholera spreads most rapidly when the earth tempera- 

 ture is high ; this happens chiefly when the ground-water 



