lVeat/ui\ IVaier and Disease. 7 



natural and invariable constituents — oxygen and nitrogen^ — in 

 certain proportions, and its accidental and variable ones. 

 Important among these is the weight of air, light, tempera- 

 ture, humidity and winds. We .shall endeavor to a.s.sess the 

 value of each of these units in its relation to its effect upon 

 the individual. Practically, there is no such actuality as their 

 acting as units, complete disassociation can not occur, nor can 

 they act in entire combination at any one period of time, 

 because, in the first supposition, there can be no severence of 

 relations established by a common derivation ; and in the 

 second ca.se the change of the earth's position in its move- 

 ments around the sun compels succession of results and not 

 simultaneity. It can not blow hot and cold at the same time. 



Probably there is no more complete correspondence than 

 that which has been brought about, in process of evolution, 

 between the structure and function of the lungs— in the abso- 

 lute necessity of the inhalation of oxygen and the exhalation of 

 carbonic-acid gas and moi.sture. Respiration mu.st be carried 

 on, and there is not left to the individual ability to modify it 

 in any wa}^ except by violent and destructive means. He can 

 not commit suicide b}' simply holding his breath, nor is there 

 any hibernation for the human animal. A certain rate of 

 respiratory movement is foreordained. The movement is 

 about eighteen to the minute in the adult human being in 

 quietude or ordinary motion. This will be modified by 

 bodih' effort, a nervous excitement, rarefied air, or high alti- 

 tudes, or disease. Provision is made for a return to the 

 normal rate on cessation of the exciting cause. There is a 

 very wide variation in the animal kingdom in the number of 

 respirations per minute, running from one in the hippopota- 

 mous to one hundred in the rat while sleeping and two hun- 

 dred waking. 



The red blood corpuscles are moving in rotation, carrying 

 their precious load of oxygen to all parts of the body, and the 

 lungs are exhaling the excretory product carbonic acid, with 

 a certain amount of moisture. While we have spoken of the 

 stability of the mechanism of respiration, the human being 

 has a limited amount of power to alter the composition of the 

 atmosphere in his immediate surroundings. There is much 

 perversity in the wa5^s by which we exclude the fundamental 



