434 INFECTION AND IMMUNITY. 



to twelve flagella situated at the ends and on the 

 sides and is actively motile under suitable condi- 

 tions. It forms no spores and is readily cultivated 

 on many media. 



The bacillus is one of the rather numerous "in- 

 testinal group" of organisms, certain members of 

 which are so similar that they can be differentiated 

 only by means of special cultures, animal experi- 

 ments, or the agglutinating, opsonic and bacteri- 

 cidal action of specific immune serums. 2 



Distribution The organism has been cultivated from earth 

 Bacillus, and infected water, and from the feces, urine, 

 blood, rose-spots and the various organs of typhoid 

 patients. In many instances in which an epidemic 

 has certainly been caused by an infected water sup- 

 ply attempts to cultivate the bacillus from the 

 water have failed. The organisms may not have 

 been included in the samples which were analyzed, 

 or, what is equally probable in certain instances, 

 they have died out in the water by the time the 

 disease was so widespread as to be considered epi- 

 demic. Its occurrence in Nature depends on the 

 distribution of the excretions of the patients and 

 carriers. The viability and virulence of the bacil- 

 viabiiity lus in water, earth, etc., vary with the nature of 

 Resistance, its surroundings. It has been found to live 

 for periods of from 2 to 4 weeks to 2 or 3 

 months in water, from 3 to 4 months in milk, 

 from 3 to 5 months in surface water, and from 

 11 to 16 months in sterilized earth; 100 days 

 in ice, from 12 to 30 days in oysters, from 50 to 



2. Of this group the bacilli of dysentery, paratyphoid 

 bacillus, Bacillus enteritidis of Gartner, colon bacillus and 

 Bacillus alcaligenes, in addition to the typhoid bacillus, are 

 the most important because of their similar morphologic and 

 cultural properties and the pathogenicity of certain of them. 



