324 TYPHOID FEVER, 



tine the surface colonies are rather more transparent than 

 those on agar. Their characters, as seen under a low 

 power of the microscope, also correspond. 



In stroke cultures on agar there is a bluish-grey film of 

 growth, with fairly regular margins, but without any char- 

 acteristic features. This film is loosely attached to the 

 surface, and can be easily scraped off. 



The growth on potatoes is most important. For several 

 days (at ordinary temperature) after inoculation there is 

 apparently no growth. If looked at obliquely, the surface 

 appears wet, and if the surface is scraped with the platinum 

 loop, a glistening track is left ; a cover-glass preparation 

 shows numerous bacilli. Later, however, a slight pellicle 

 with a dull, somewhat velvety surface, may appear, and this 

 may even assume a brown appearance. These characteristic 

 appearances are only seen when a fresh potato with an acid 

 reaction has been used. 



In bouillon incubated at 37 C. for twenty-four hours, 

 there is simply a uniform turbidity. Cover-glass prepara- 

 tions made from such sometimes show filamentous forms of 

 considerable length, without apparent segmentation. 



Conditions of Growth, etc. The optimum temperature 

 of the typhoid bacillus is about 37 C., though it also 

 flourishes well at the room temperature. It will not grow 

 below 9 C. or above 42 C. Growth takes place in 

 anaerobic as well as in aerobic conditions. Its powers 

 of resistance correspond with those of most non-sporing 

 bacteria. It is killed by exposure for half an hour at 60 

 C., or for two or three minutes at 100 C. Typhoid bacilli 

 kept in distilled or in ordinary tap water have usually been 

 found to be dead after three weeks (Frankland). 



The Bacillus Coli Communis. This bacillus is the chief 

 organism present in the small intestine in normal conditions, 

 and, with many other bacteria, it also inhabits the large 

 intestine. During typhoid fever, and other pathological 

 conditions affecting the intestines, it is relatively and abso- 

 lutely enormously increased in the latter situation, where it 

 may sometimes be almost the only bacillus present. Its 



