156 BACTERIA IN RELATION TO DISEASE 



juice, and therefore of its antiseptic power, such as occurs from immoderate 

 eating or drinking, or from climatic causes in summer. Every gastric or 

 intestinal disturbance will be a predisposing condition. 



The Koch ' comma ' bacillus ( Vibrio cholcrac, Figs. 28, k ; 2, c ; 5, d \ 6, 

 a-c] is, like other vibrios, a minute curved, actively motile rod (2 ju, by 04^), 

 bearing a cilium at one end. Occasionally two cilia are present, never more. 

 On the surface of fluid media (bouillon or asparagine + sugar solution) 

 the organism, being aerobic, forms thin membranes, and at the same time 

 renders the underlying liquid turbid. Besides the more numerous single 

 vibrios, long or short motile chains occur. These have been described as 

 spirilla, but are really nothing but chains of vibrios joined end to end 

 (Fig. 28, k}. True endospores. although doubtlessly produced, are not 

 yet known. Perhaps sporulation takes place only under tropical con- 

 ditions of life. The structures found in old cultures that have been 

 described as spores are only due to involution and granular degeneration 

 of the cell-contents, as is evident from the extraordinary shapes of the 

 cells. 



The sporeless comma bacilli of our cultures can endure drying only for 

 a very short time, perishing in a very few hours. A dry resting-stage as in 

 the tubercle bacillus is therefore wanting, and infection from dry material 

 impossible. As a metatrophic organism, however, it can live in water for 

 weeks, and is by no means tied down to peptonized food-stuffs. The table 

 on p. 55 shows it to be an ammonium bacterium that thrives well in gly- 

 cerine sal-ammoniac solution if the reaction be suitable. Acidity arrests 

 growth at once. These facts make it clear how the cholera germ is able to 

 live and multiply in dejecta, on moist soiled linen, or in water containing 

 putrescible substances. From albuminous compounds (in peptone broth, for 

 instance) the cholera bacillus forms indol and other putrefaction products, 

 while from sugar it can produce lactic acid. 



From contaminated river or well-water used for drinking or for house- 

 hold purposes the bacillus reaches the stomach and intestine by way of the 

 mouth. It is therefore of the highest importance that all drinking-waters 

 should be under strict surveillance. 



In its morphology and in its metatrophic mode of life the cholera vibrio 

 resembles our indigenous European aquatic vibrios (141), and in summer it 

 is, like them, able to live in rivers and ponds. It is, however, originally 

 a tropical organism, its native place being the East Indies, where it lives in 

 foul water just as its relatives do with us. Under such circumstances only a 

 high temperature, 30- 40 C., is necessary to permit it to thrive and develop 

 its virulence. This condition is present in our climates in summer. Some 

 of our indigenous vibrios, V. berolincnsis and V. danubicus, can develop patho- 

 genic properties, but it is not known whether they are ever the cause of 

 disease in human beings. That the tropical species are the more virulent 



