362 A MANUAL OF BACTERIOLOGY 



by centrifuging and without culturing, were added to 

 the water, the number of bacilli was reduced by 99'99 per 

 cent, after a week, and after ten days the organism 

 could not be isolated from 100 c.c. of the infected water, 

 indicating that the uncultured bacillus rapidly dies in a 

 natural water, and that even a week's storage of water 

 affords enormous protection against water-borne typhoid. 

 In aerated (C0 2 ) waters the B. typhosus does not survive a 

 fortnight. The methods of isolation from water are given 

 in Chapter XXI. 



The Bacillus typhosus may gain access to shell- fish, 1 

 oysters, mussels, cockles, etc., particularly if obtained 

 from sewage-polluted laying. Such polluted shell-fish 

 may give rise to typhoid epidemics as at Winchester 

 and Southampton in the case of oysters, and in the case 

 of cockles, derived from the Thames Estuary and imper- 

 fectly cooked, to typhoid cases. Buchan found that out 

 of 855 primary cases of typhoid fever occurring in house- 

 holds in Birmingham, 124, or 14-5 per cent., had a history 

 of mussel eating, and in seventeen instances the histories 

 were conclusive of mussel infection. Mussels, under 

 certain conditions (which are not well understood), are 

 liable to develop mytilotoxin, etc. (p. 38), which gives rise 

 to gastro- enteritis. Shell-fish from sewage-polluted layings 

 contain B. coli in varying numbers, but from uncontami- 

 nated layings are free from this organism, which may 

 therefore serve as an index of pollution (see " Examination 

 of Shell-Fish," Chapter XXI). Contaminated shell-fish, 

 removed to pure water, gradually cleanse themselves 

 probably after two to three weeks' sojourn. Klein obtained 

 the typhoid bacillus from artificially infected oysters, kept 



1 On pathogenic organisms in shell-fish see Reports by Bulstrode to 

 the Local Government Board, 1894 and 1911 ; Rep. Med. Off. Loc. Gov. 

 Board for 1899-1900, p. 574 ; Houston, Fourth Report of the Sewage 

 Commission., vol. iii, 1904 ; McWeeney, Loc. Gov. Board, Ireland, 1904 ; 

 Buchan, Journ. cf Hygiene, vol. x, 1910, p. 569. 



