METABOLISM 67 



like or nitrogenous compounds as by-products of 

 normal metabolism, and these, unless removed by 

 excretion, poison and eventually kill the organism 

 that produces them. 



Another group of substances, called anaesthetics, 

 of which chloroform and ether are the most familiar, 

 depress the activities of protoplasm and, if not 

 counteracted, kill it. The action of such substances 

 is still a matter of debate, but since all of them are 

 fat solvents, it has been supposed that their poisonous 

 action may be exerted on the fatty components of pro- 

 toplasm. The poisonous action of these substances 

 is of a different character from the depressant action 

 mentioned. If the action of the anaesthetic is not 

 too violent or too prolonged, the protoplasm will 

 later recover its activities and resume its functions 

 as before. It has been shown that, whereas the 

 action of poisons (including such substances as 

 ether and chloroform in poisonous doses) greatly 

 increases the permeability of the cell membrane, 

 the merely anaesthetic effect is accompanied by a 

 temporary decrease of permeability. 



Antiseptics. Nearly all the disease and physical 

 suffering that man is subject to is the result of the 

 activity of microorganisms that find lodgment 

 within the body, and, rapidly multiplying, produce 

 poisons that affect the whole system. We combat 

 these by the use of such poisons as have been men- 

 tioned above, chemicals that either inhibit the 

 growth of the organisms or destroy them. Especially 



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