MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 795 



of the single organism. It is quite regular in shape, straight with rounded ends. 

 The baciUi usually occur singly; occasionally two may be attached end to end for a 

 short time. There are ten to fourteen comparatively stout flagella about two or 

 three times the len^h of the organism peritrichic in their arrangement. There 

 are no capsules and no spores. They stain with all aniline dyes, and not infre- 

 quently exhibit more deeply staining areas at the poles. They are Gram-negative. 

 Biological and biochemical characters. The minimum temperature is about 10° 

 the optimum 37°, maximum 40 to 41°. It is aerobic and facultatively anaerobic, , 

 The slight preference for oxygen is probably of little account when such sugars as 

 glucose are present. The bacillus is not very sensitive to the reaction of media and 

 will grow in the presence of either slightly alkaline or acid reaction. Alkaline 





X 



Fig. 167. — Bacillus of typhoid fever. X 1000. (After Williams.) 



substances are produced from peptone. Acid is formed from dextrose, levulose, 

 galactose, mannit, maltose, and dextrin. Lactose and saccharose remain un- 

 changed. Gas is never formed. It is the rule that the Bacillw typhosus does not 

 form indol; certain strains, however, form a trace. The toxins of the bacillus have 

 been very widely studied and several different opinions are held with regard to 

 their nature. Most evidence supports the idea that the poisons are only set free 

 by the destruction of the bacterial bodies. This may be brought about experi- 

 mentally by various means such as the use of lytic or bactericidal sera, by the 

 disintegration occurring in old cultures, by extraction under great pressures, by 

 triturating after freezing in liquid air and by emulsifying cultures, sterilizing by 

 heat then extracting with salt solution. These endotoxins, however obtained out- 

 side 'of the host, have been found to produce by injection into animals only lytic 



