MICROBIAL DISEASES OF MAN AND ANIMALS. 643 



chemical characters. The minimum temperature is about 10 the optimum 37, 

 maximum 40 to 41. It is aerobic and facultatively anaerobic. The slight prefer- 

 ence 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 pres- 

 ence of either slightly alkaline or acid reaction. Alkaline substances are produced 

 from peptone. Acid is formed from dextrose, levulose, galactose, mannit, maltose, 

 and dextrin. Lactose and saccharose remain unchanged. Gas is never formed. It 

 is the rule that the Bacillus 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 experimentally 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 outside the host, have been found to produce by injection into animals only 

 lytic and bactericidal sera and not an antitoxin. More recently, however, some ob- 

 servers claim to have shown in comparatively young cultures the presence of a sub- 

 stance which upon injection into animals yields an antitoxin and thus comports itself 

 after the manner of a true diffusible or soluble toxin. Agar streak cultures show an 

 abundant filiform whitish or bluish-gray translucent growth with no special character 

 istics. Broth is uniformly and moderately clouded and only occasionally a delicate 

 pellicle may develop. Gelatin colonies are bluish white in color, transparent and with 

 somewhat notched margins. Stab cultures show more growth at the surface, while in 

 the depth the growth is filiform and less abundant. The medium is not liquefied. 

 Milk is not coagulated. In litmus milk there may be a trace of acid formed at first, 

 followed by a return to neutral or very slightly alkaline reaction. Potato was at one 

 time considered a very valuable differential medium. The growth of the bacillus 

 upon it is quite abundant, glistening, but invisible, when the potato is acid. A more 

 alkaline reaction allows a rather heavy yellowish growth indistinguishable from B. coli. 

 Special media are used in the cultivation of the typhoid bacillus, chiefly for differential 

 purposes. The cultural features on these do not show sufficiently striking characters 

 to make it worth while to review the many that have been devised. Specific agglutinat- 

 ing and bacteriolytic sera as well as the complement binding reaction are valuable 

 aids in identifying the bacillus. Resistance to heat and light is not different from 

 that of the average non-spore-bearing species. Its thermal death-point is about 56 

 for ten minutes, 60 for one minute. Exceptionally resistant forms have been found 

 alive in ice after three months. Sometimes the bacilli will remain viable for a month 

 after drying. At other times they die out rapidly. They have been found to be 

 viable for ten days in distilled water, while pure sodium chloride dissolved exerted an 

 unfavorable influence. In faeces the length of life is from a few hours to several days, 

 or even as high as five months in winter. Their Me in privies and cesspools is ordi- 

 narily brief but has been found to extend for thirty days. Of the non-spore-formers 

 the bacillus appears to be rather more resistant than the average but succumbs within 

 five minutes to 1:5000 mercuric chloride or 5 per cent phenol. 



