176 SPECIAL BACTERIOLOGY 



Kashida has recently observed that the acid produced by the colon 

 bacilli in cultures becomes neutralised in a little time, an alkaline 

 reaction soon appearing, which was so strong that colonies on litmus 

 milk sugar agar plates were coloured an intense blue, and when rosolic 

 acid was used as a reagent, the colonies were coloured red. With the 

 Bacillus typhi abdominalis the above characteristic is awanting. Investi- 

 gations of the condensation water of agar cultures showed that the 

 alkaline reaction of the colon bacilli was due to the formation of ammonia. 

 This was very distinct in cultures on 1 \ per cent, meat infusion agar to 

 which 2 per cent, milk sugar, 1 per cent, urea, and 30 per cent, litmus 

 tincture were added. 



BACILLUS EQUI INTESTINALIS. 



Found by Dyas and Keith in the intestines of a horse. It is 

 distinguished from the coli communis as follows : It is somewhat thicker, 

 does not grow at a low temperature, and in fermentation tubes produces 

 no gas, but it coagulates milk in one to two days. 



Systematic examination of the alimentary contents of both man and 

 animals shows that numerous bacteria are present ; but Nuttall and 

 Thierfelder discovered in a course of experiments that animals could 

 live without the presence of bacteria in the alimentary canal. The 

 experiments were conducted with young guinea-pigs, which were born 

 by Ccesarean section to prevent bacteria entering their economy, nourished 

 with sterile food, killed in eight days, and examined for bacteria, the 

 results being negative. 



INFLUENZA. 



Pfeiffer discovered the bacillus and isolated it in pure cultures 

 during the epidemic in 1891-92. Pfeiffer's discovery has been fully 

 confirmed by others. 



Microscopical Appearances. Extraordinarily small bacilli (0-2 to 

 0'5 ft), and only two to three times as long as broad, with rounded ends. 

 It very seldom forms threads in sputum, but frequently in fresh pure cul- 

 tures ; in three to four-day-old cultures involution forms are already 

 visible.' Two particularly small bacilli are frequently observed arranged 

 close together, causing them to be easily mistaken for diplococci. (For 

 Photomicrograph of the bacilli in sputum, see Fig. 65.) 



Motility. Non-motile. 



Spore Formation does not appear to exist ; it has never been ob- 

 served in either secretions or cultures, and, moreover, the bacillus exhibits 

 only slight resistance to heat or drying. 



