820 THE POPULAR SCIENCE MONTHLY. 



lete is, therefore, first the good oxidizer (see M. Foster, page 628), 

 the person who has good lung capacity, and especially a powerful 

 heart to drive the blood swiftly ; and, secondly, the person who 

 trains well, whose tissue is healthy and firm and does not break 

 down rapidly into waste — waste in his case not outstripping the 

 powers of oxidation, and thus causing distress. On the other 

 hand, the untrained man, who breaks down in the race with every 

 symptom of distress, is the poisoned man — the man who formed 

 waste quicker than he could oxidize it.* 



Reviewing, then, what we have said, we seem to see three 

 things : first, that so long as we have a sufficiency of oxygen, we 

 get rid of a large amount of daily waste in safe and harmless 

 forms ; secondly, that when oxygen is withheld from us there are 

 poisons in every part of our tissue of so deadly a character (either 

 abnormally formed because oxygen is absent, or under ordinary 

 circumstances neutralized by the supplies of oxygen present) as 

 to take life in a few minutes ; thirdly, that even when all is well, 

 and our system is functioning under healthy conditions, we are 

 still always breathing out from ourselves, through lung and 

 through skin, certain dangerous poisons, which poisons, when we 

 are living in bad air, we perpetually reabsorb into ourselves, to 

 our own great hurt. 



Nothing, however, that we have said satisfactorily explains the 

 presence of these poisons which escape from the lungs and the 

 skin. It seems hard to explain why, when Nature so successfully 



* In such a case it may be asked, Why are not the waste poisons passing into the 

 blood from the tissues safely got rid of in the form of carbonic acid and water when the 

 blood reaches the lungs ? It seems difficult to escape from the conclusion (see Foster, p. 

 603) that these unoxidized waste products may, on occasion, pass the lungs without being 

 got rid of. In the case of violent exercise, it would seem that the quickened heart and 

 quickened breathing must come from the action of waste poisons, which, passing the lungs, 

 reach the medulla and stimulate the nerve-centers, there not having been time, owing to 

 the excessive quantity of waste produced, to reduce all the waste to the safe final prod- 

 ucts of water and carbonic acid, and therefore some part of the waste in an unoxidized 

 state being carried past the lungs on to the nerve-centers. As regards the poisons we re- 

 breathe from the air, it is, of course, rather a surprising thing, if they entered the circu- 

 lation, that they should not be oxidized in the blood when we think of how they must be 

 surrounded by the oxygen that the blood has received from the air. But active as oxygen 

 is— in its " nascent " state, just released from haemoglobin— in the tissues after leaving the 

 blood, there are reasons for thinking that this activity does not exist in the blood itself. 

 Thus we are told that pyrogallic acid, which is an easily oxidizable substance, may pass 

 through the blood without undergoing any change ; and fresh blood, as we are told, has 

 little oxidizing effect. This strange powerlessness of the oxygen in the blood increases 

 the danger of these waste poisons. If they were oxidized in the blood we should be able 

 probably to got rid of them quite harmlessly, as they would not be in the condition of 

 poisons when they escaped from lungs and skin ; but we may feel sure that there is some 

 good reason why this can not take place. When they are once carried to the tissues, ex- 

 cept in the case of persons taking plenty of exercise and leading a healthy life, there may 

 be no superabundance of oxygen, but rather a deficiency, for all the work to be done. 



