XIV 



tact with wounds without doiiif^ harm because, unless the con- 

 dition of their victims is favourable to their multiplication, they 

 are innocuous. Some of our most healthful and enjoyable 

 occupations expose us continually to their attacks, and yet how 

 seldom — how very seldom considering the circumstances — do 

 persons suffer from tetanus. The bacillus of tetanus abounds in 

 most kinds of soil, and so almost universal is it that M. Bassano, 

 who obtained soil "from forty-three different regions in various 

 parts of the globe, got positive results with twenty-seven of 

 them." White mice and guinea pigs were inoculated with these 

 forty-three samples of soil and in twenty-seven tetanus was pro- 

 duced in from two to four days. Like many other persons I have 

 been a gardener all my life, and when engaged in this pastime 

 almost invariably have scratches and abrasions on my hands 

 which are wholly unprotected from contact with the soil, and yet 

 for half a century I have escaped the dangers of tetanus although 

 in garden soil the tetanus bacilli are so abundant that — " Speak- 

 ing colloquially, a worker at the Brown Institute told a friend 

 that they grew the tetanus bacillus in the garden there." How is it 

 then that we enjoy this immunity from the attacks of these 

 enemies which surround us on all sides ? It is because Nature, 

 which allows these bacilli to exist ni such countless numbers, 

 provides also a protection against their deadly attacks. The 

 bacilli, which are multiplied by spores, are anoerobic ; they can- 

 not live when exposed to the oxygen of the air. In their germ 

 condition they are not sensitive to oxygen ; but when spores are 

 introduced into a wound and the bacilli are hatched, there is the 

 danger to them of being destroyed by the oxygen with which 

 they are liable to come into contact, and it is only in a particular 

 condition of the wound that they can multiply ; on its actual 

 surface the oxygen of the air destroys them ; immediately beneath 

 the wound they are exposed to a similar risk from the fresh, 

 supplies of oxygen to the tissues which are being constantly 

 brought up by the red corpuscles of the blood. They flourish 

 only in "a condition of anoerobiosis, or oxygen famine," and here 

 alone are they able to generate the ptomaine, the virulent 

 poison which is the cause of tetanus. The extent to which we 

 are naturally protected is suggested by ^Yoodllead when he says- 

 — " It is an undoubted fact that failures to produce tetanus with 



