8i6 THE POPULAR SCIENCE MONTHLY. 



Now let us take the case of a person who sits in a closely shut 

 up room, ten feet high, ten feet broad, and fifteen feet long, for 

 five hours.* At the end of that time he is breathing air which 

 contains 1*2 i^er cent less oxygen than it ought to contain, but, 

 what is far more serious, he is breathing some air which has 

 already passed through his lungs, and which is charged with this 

 special poison. Here is the great secret of the fatal mischief. 

 Nature has got rid of the poison, thrown it out of the system, 

 but the perverse occupant of the room insists on thwarting Na- 

 ture, and, by means of his closed doors and windows, breathes in 

 again, it may be a second time or a third time, the poison that has 

 once been safely got rid of. Say that in twenty-four hours 500 

 cubic feet have passed once through the lungs, then in six hours 

 our friend will have vitiated one quarter of that quantity, or 125 

 cubic feet — i. e., one twelfth of the whole air in the room (1,500 

 cubic feet). If he still goes on sitting in his study, at the end of 

 nine hours he will have vitiated 187*5 cubic feet, or one eighth of 

 the whole ; or, if he has been unfortunate enough to have a friend 

 sitting with him, then in six hours they will have tainted one 

 sixth of the air ; and of every mouthful of air they breathe after 

 that time, one sixth of it must be supposed to be charged with 

 poisons that have been already once got rid of, but are now being 

 retaken into the system. Of course, this proportion of one sixth 

 will not remain constant. Each breath expired will make the 

 matter worse. 



A few words seem necessary here for those who have never 

 followed the changes going on in the body. We know that we 

 are constantly building up new tissue of difl'erent kinds, and that 

 this building up makes it necessary that the old tissue should be 

 got rid of. The larger part of our food measures this change 

 which is going on. If we take our daily food, liquid and solid, 

 for twenty-four hours, as weighing about five pounds eight ounces 

 (Hermann, page 233)— a large proportion being water— we may 

 look upon about five pounds three ounces of this quantity as used 

 for the making of new tissue, the other five ounces forming what 

 is spoken of as exhausted ferments, and which, passing along the 

 alimentary canal, is eventually rejected. Now, all the suitable 

 part of the food, after undergoing various changes, which are 

 necessary to prepare it for its passage from dead food into living 

 tissue, finds its way into the blood ; and when by means of the 

 larger blood-vessels it reaches the very minute blood-vessels, 

 called capillaries, it pours a part of itself out through the per- 



* A considerable quantity of air, however, is always entering through window frames, 

 under doors, even through brick walls. On the other hand, we have made no allowance 

 either for space occupied by furniture or for the (probably) tainted condition of the 



