826 THE POPULAR SCIENCE MONTHLY. 



and purer air being heavier than the heated impure air, and 

 therefore nearer the line of the floor. 



Animals furnish the same evidence. Cows and horses both 

 suffer grievously from want of ventilation in their stables ; and 

 cattle, though they require warmth for fattening, still put on 

 flesh better in a colder but well-ventilated place than in a warmer 

 place which is unventilated (Parkes, page 180). So also Parkes 

 tells us about the French cavalry. Before 1836 the mortality 

 among the horses varied from 180 to 197 per 1,000 per annum. 

 With the enlargement of the stables and increased quantity of 

 air, the loss was reduced to G8 per 1,000, and finally to 28^ per 

 1,000, and of officers' horses to 20. 



Then we have the evidence of the ordinary tests for ascertain- 

 ing the purity of the air. Air fouled by respiration discolors 

 permanganate of potash and robs it of a portion of its oxygen ; the 

 amount of organic matter is then measured by the number of 

 volumes of oxygen required to reoxidize the permanganate and 

 restore it to its former condition. Another test is the presence of 

 certain bacteria, which are found in large numbers in foul air, 

 increasing out of proportion to the molds or fungi found in the 

 air, which appear to be much less affected by impurities. It is 

 stated that these forms of life all originally come from the open 

 air — that reservoir of all things — though they are supposed to 

 multiply in congenial quarters when once they have found an 

 entrance. The significant fact, however, is their number, which 

 might seem to show that they prosper just because they have dis- 

 covered their proper food — the organic poison which Is poured 

 out into the air from our lungs and skin. On this point. Dr. A. 

 E-ansome makes an interesting sj^eculation, which we quote from 

 memory — a wrong thing to do. Impressed with the belief that 

 consumption is communicable in foul air, and non-communicable 

 in good air, he believes that the bacillus (a form of bacteria) which 

 conveys the disease retains its virulence more in foul air than in 

 pure air, and is thus better able to make a lodgment in the human 

 system.* — Contemporary Review. 



[To he concluded.^ 



* This speculation of Dr. A. Ransomc's suggests another speculation. Dr. Klein (pp. 

 238-248) believes that in the interior of healthy human tissue no bacteria, which cause 

 putrefaction, are found. They are found abundantly in those parts of the system to which 

 air penetrates, as, for instance, in the mouth, or in the alimentary canal ; and from the 

 alimentary canal they pass easily, as the food itself does, into the diminutive blood-vessels 

 or the diminutive lymphatics (locally called lacteals) that line the walls of this canal. Cut 

 if the blood is in healthy order they seem to perish, dying for want of food. Dr. Kliin 

 goes on to state that if at some point they are carried to tissue that is in an unheal. by 

 condition, there they may obtain a footing and begin to multiply. He does not actually 

 state, as we understand, that the unhealthy condition of the blood keeps them alive, but 

 he implies it ; and it would seem probable that the unhealthy state of the blood^ — for ex- 



