TYPHOID AND SOIL 147 



growth of the bacillus of typhoid in soil of an ordinary field. By 

 experimental inoculation of the soil with broth cultures, he was able 

 to isolate the bacillus twelve months after, alive and virulent. He 

 concluded that the typhoid organism is capable of growing very 

 rapidly in certain soils, and under certain circumstances can survive 

 from one summer to another. The rains of spring and autumn, or 

 the frosts and snows of winter, do not kill it off so long as there is 

 sufficient organic pabulum. Sunlight, the bactericidal power of 

 which is well known, had, as would be expected, no effect except 

 upon the bacteria directly exposed to its rays. The bacillus typhosus 

 quickly died out in the soil of grass-covered areas.* 



Next came the experiments of Dr -Sidney Martin, which were 

 undertaken to inquire into the extra-corporeal existence of the 

 bacillus of typhoid fever in soil. He found, after a prolonged 

 research, that certain cultivated soils, especially garden soils, when 

 sterilised are favourable to the vitality and growth of this bacillus, 

 whether the soil was kept at room temperature (19 C.) or blood-heat 

 (37 C.). In such soils the B. typhosus was still alive after four 

 hundred and four days, and remained alive, though not for a long 

 period, if the soil were dried and reduced to dust. If, however, the 

 bacillus is added to a well-moistened but not sloppy cultivated soil, 

 it rapidly dies, and is usually not obtainable two days after being 

 sown in it, and its disappearance appears to be more rapid the higher 

 the temperature, which is probably due to the rapid growth of 

 ordinary soil bacteria. If the cultivated soil is not made very moist 

 when the B. typhosus is added, the organism can be recovered from 

 the soil up to twelve days after it has been added. Lastly, if this 

 bacillus is added to natural uncultivated soils which have not been 

 sterilised, it ceases to exist within twenty-four hours. Martin holds 

 that the reason of the rapid disappearance of the typhoid bacillus 

 from natural unsterilised soils is probably twofold. First, there is 

 the antagonism of the soil bacteria, many of which are putrefactive ; 

 and secondly, the typhoid bacillus requires for its growth nitrogenous 

 substances, usually in the form of proteids. Cultivated soil is dis- 

 tinguished from uncultivated soil by containing more nitrogenous 

 organic matter in the form of nitrates and ammonia, and also more 

 partially changed proteid substances. Hence it is a more favourable 

 environment for the typhoid bacillus. As a general result of these 

 investigations, it may be concluded that the typhoid bacillus has, 

 commonly, only a short existence in the soil, being destroyed by the 

 products of the putrefactive bacteria which exist in most cultivated 

 soils.f 



* Brit. Med. Jour., 1898, i., pp. 69-71. 



t Reports of Medical Officer to the Local Government Board, 1898-99, pp. 382412 ; 

 1899-1900, pp. 525-548 ; 1900-01, pp. 487-510. 



