TEXT-BOOK OF BACTERIOLOGY. 273 



Man evidently stands in the foreground of events, and the soil 

 at most occupies an occasional place in the circulation from the 

 human intestine through the ingesta and to the human intestine 

 again. 



This view certainty corresponds to the actual conditions. Nu- 

 merous single observations have proved with sufficient certainty 

 that man is the real source of infection. The very fact that the 

 contagious spread of the disease follows man and travels with him 

 is a firm support for the view just discussed, whose direct proof 

 can hardly be demanded and furnished for every case. 



We know that the bacteria are found in the intestine during the 

 disease; their appearance, in fact, coincides with the commencement 

 of the infection. Their increase very soon reaches its maximum at 

 the same time the symptoms of the disease do. The intestine con- 

 tains a nearly pure culture of the comma bacilli. They begin to 

 die after two to three days and to make room for the real inhabi- 

 tants of the intestine, the septic bacteria. This terminates the 

 process essentially and a cure may, under some circumstances, take 

 place. 



The existence of bacteria outside the intestine may also be 

 proved in the copious discharges of the patients; it has been ob- 

 served more rarely in the vomited matter, presumably only in such 

 cases where intestinal contents found entrance to the stomach. 

 The micro-organisms keep their vitality for a long time, as they 

 remain capable of development in a moist condition for months 

 even* without possessing spores. They do not fall a prey to resulting 

 putrefaction because man, who throws the excrements into water,, 

 dilutes them as much as possible, transfers them with his fingers to- 

 new media, soils the linen with them, and thus affords the bacteria- 

 protection from harm and opens many ways of spreading the 

 disease. 



The comma bacilli have been found in water even under natural 

 conditions ; besides, experiments have shown that they do not 

 merely live in it, but can even increase. We may succeed in produc- 

 ing pure cultures on damp pieces of linen; and it is not impossible that 

 even the upper strata of the earth perform the service' of the go- 

 between at times, and aid in transmitting the poison; but this may 

 occur in exceptional cases only and on the condition that they are 

 thoroughly moistened; for the comma bacillus thrives only in mois- 

 ture, dryness being a more impassable obstacle to it and constitu- 

 ting a better protection against advance than institutions of dis- 

 infection and weeks of quarantine. 



It is true that various facts regarding their appearance and the 

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