I.] THE HISTORY OF THE COMMA-BACILLUS. 17 



their dying. We know also of other infectious substances 

 with whose nature we are not yet accurately acquainted, for 

 example, the infectious matters of small-pox and of vaccine, 

 which can be kept in a dried state for several years, still 

 retaining their power of infection. If now the comma- 

 bacilli, which, as such, are very speedily killed by drying, 

 pass into a resting condition under some circumstances, 

 that would very soon be shown during the process of 

 drying. 



" This is always one of the most important questions in 

 the etiology of an infectious disease, and especially so of 

 cholera. The investigation of this point has therefore been 

 made in the most careful manner possible, and by every 

 possible method, and I hardly think that anything more can 

 be done on this point. Above all, cholera-dejecta and the 

 contents of the intestines of cholera-corpses were left in a 

 damp condition on linen, in order that the comma-bacilli 

 might develop under the most favourable circumstances. 

 After certain intervals of time, pieces of the linen were 

 dried for example, after twenty-four hours, after a few 

 days, after several weeks to see if during this period any 

 condition of permanence had been established. For 

 infection through cholera-linen affords the only undisputed 

 example of the presence of an effectual infectious substance 

 which adheres to a special object. If there were a permanent 

 or resting state to be found anywhere, it must have been 

 found on cholera-linen. 



"But in none of these cases was a permanent state 

 discovered. When the dried objects were examined, it was 

 seen that the comma-bacilli had died off. Then, further, 

 the dejecta were placed in earth, being either mixed with 

 earth or spread on the surface, which was either kept dry 

 or moist ; they were mixed with marsh- water ; and were 



c 



