THE BASIS OF LIFE 21 



its carcass into air and soil. Birds and insects may interrupt 

 their work, u They may steal portions of the derelict, use them 

 for fuel, or patch them between their own ribs. But they, too, 

 will soon lie breathless on the ground ; and the bacteria are 

 always ready to finish their interrupted task. Why should 

 they wait until the slight change occurs, important to us, but 

 of little consequence to them, which marks the transition of 

 living protoplasm into dead proteins ? There is nothing in 

 the constitution of protoplasm which makes it harder to break 

 up than protein. There is no quality inherent in living matter 

 which makes it resistant of decay. We resent the officiousness 

 which prompts bacteria to obtain entrance into the ship while 

 it is still under full sail, with a view to commencing the work of 

 demolition. Deep in our minds lies the conviction that it is 

 contrary to the rules of Nature. We are especially annoyed at 

 the many ruses bacteria adopt to disguise their personalities. 

 The bacteria of the soil we can keep at a proper distance. But 

 bacteria of the stream, bacteria of milk, bacteria of the breath 

 that would betray us with a kiss ! It is hard to recognize 

 that they are fairly and squarely playing their part. Birds 

 and insects we can beat off with our hands. Our invisible 

 enemies are everywhere. They are constantly insinuating 

 themselves through scratches in the skin, through abrasions in 

 the mouth, through surfaces of the intestine left unprotected 

 owing to the desquamation of its epithelium. But if we are 

 constantly open to attack, we are policed by myriads of zealous 

 leucocytes, ever ready to reduce the invaders to impotence. 

 The germs which have found entrance fire off a toxin. The 

 leucocytes reply with an antitoxin. There is absolutely no 

 limit to the power of protoplasm to protect itself, if only it be 

 not taken by surprise. It can resist any organic poison if it is 

 allowed a sufficient time to produce the antipoison. The ferment 

 of pancreatic juice, trypsin, is a poison which is unlikely to find 

 its way into the blood. When injected it produces disastrous 

 results owing to its immense activity in digesting proteins. 

 An animal " prepared " by the injection of successive doses 

 of trypsin develops an antitrypsin. Injection of pancreatic 

 juice no longer does it any harm. Tapeworms which live in 

 the intestines ^are bathed in pancreatic juice ; they are con- 

 stantly exposed to its digestive action. They are not digested, 



