ANAEROBIC ORGANISMS 113 



alcohol they produce ultimately poisons them, and this is true 

 of many anaerobic bacteria. It had been known for some 

 time that the bacterium causing lock-jaw, tetanus, was one 

 of these anaerobes, and in the distribution of such organisms 

 the soil, especially if highly manured, plays a great ])art. 

 There is no free oxygen, or practically none, in the alimentary 

 canal, and many of the bacteria that live there are anacrol)ic. 

 Many anaerobes are extraordinarily poisonous; and during 

 the war the extensive character of the wounds caused by 

 shell splinters or contaminated by the earth gave ample 

 opportunity for infection. Gas-gangrene, for instance, was 

 caused by one of these organisms, Bacillus welchii, and during 

 the first months of the war it was very difficult to deal with. 

 Another one is Bacillus hotulinus, which occurs from time to 

 time in potted meats and vegetables, and as we have recently 

 seen, may be the cause of sporadic outbreaks of very fatal 

 disease. 



But the power to exist without oxygen is by no means 

 confined to the lower animals. We have said above that there 

 is practically no free oxygen in the intestine, and yet many 

 worm-like organisms live therein. Tapeworms which attain 

 a length of 36 metres, and round- worms which may attain 

 a length of from 16 to 45 centimetres and a breadth of 

 6 millimetres, live in the intestine in an atmosphere devoid 

 of oxygen. I have myself taken from the air-bladder of a 

 rainbow trout, caught in a stream on Lord Knutsford's estate 

 near Royston, a number of perfectly healthy round-worms. 

 An analysis of the air in the trout's air-bladder, immediately 

 after death, gave the following results : 



Carbon dioxide 1-5 per cent. 



Oxygen 0-0 per cent. 



Nitrogen 98-5 per cent. 

 There was not the faintest trace of oxygen, and yet the round- 

 worms flourished and bred. There is still very much to be 

 learned about the metabohsm of these highly developed 

 creatures which live in an oxygen-free atmosphere. It has 

 been shown in the case of the two round-worms, Ascaris 

 mystax and Ascaris megalocephala, which live in the intestines 

 of the cat or dog and of the horse respectively, where the 



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