POP UL AB SCIENCE 



THE BREATH. 



BY DR. PETTIGREW. 



By " the breath" is meant, that portion of 

 the surrounding atmosphere that is taken 

 into the body. It there undergoes a change, 

 issuing as a gas different from the combina- 

 tion of gases taken in. There is constantly 

 going forward a waste or consumption of 

 materials; no motion can take place — the 

 moving of the finger, tongue, or eyelid — 

 without a waste of material. This noxious 

 waste matter is carried off by the blood, 

 which receives something in its place— oxy- 

 gen, the supporter of life, as it is of light. 

 Just as the burning candle deposits carbon 

 on the inner side of a glass put over it, and 

 is speedily extinguished if the glass be not 

 removed to admit a fresh accession of oxy- 

 gen — so do the tissues of the body, con- 

 stantly burning as it were, send forth car- 

 bon, and require a fresh supply of oxygen. 

 Blow through a tube into a glass of lime 

 water, which has a great affinity for carbon, 

 and it will be discolored, just as if carbon 

 had been introduced by flame. The use of 

 the lungs, that is, the membrane over which 

 the blood-vessels pass, and to which they 

 carry blood, is to expel the carbonic gas, 

 and receive back oxygen from the atmo- 

 sphere. This is done in all animals ; in 

 some by mere tubes, in others by bags, and 

 in others by a series of little sacks. In the 

 caterpillar, for instance, there is a simple 

 tube ; in the butterfly a series of tubes, in 

 the lines crossing its wings, serving at once 

 to give buoyancy, the air becoming rarified 

 by the heat of the insect's body, and as 

 organs of respiration : an illustration, often 

 found, of one provision serving two pur- 

 poses — ■ 



" In human works, though labored oft with pain, 

 A thousand movements scarce one purpose 

 gain: 

 In God's, one can its proper end pro luce, 

 And serves as second to some other use." 



So with the burrowing beetle, working in the 

 earth, it requires several large bags, or dis- 

 tended tubes, as reservoirs of air. For 

 animals that live in water, there is a similar 

 apparatus. Water contains the atmosphere 

 in a state of solution. Fishes have a pecu- 

 liar apparatus to separate the one from the 

 other, so as to respire the air without swal- 

 lowing the water ; therefore it is that they 

 will not live in either stale or distilled water, 

 the oxygen having been consumed or ab 

 stracted. The current of water forces open 

 their gills, a sort of membrane, through 

 which the oxygen passes into the blood. 

 Hence they cannot live on land ; they die, 



not from want of water, but of air ; if their 

 gills were opened for them, they could con- 

 tinue to breathe. The frog is greatly as- 

 sisted in breathing by his porous skin ; as 

 indeed is man. The crocodile gets the ad- 

 vantage of his antagonist by dragging him 

 into the water, where he can breathe so long 

 as he has the tip of one jaw above water ; 

 tubes leading from two orifices there into 

 his lungs. Birds have, for a purpose similar 

 to that of the butterfly's tubes, hollow bones, 

 at once lessening their specific gravity and 

 feeding with breath. 



The human lungs are also tubes, but with 

 thousands of dilations. They are contained 

 in what is significantly called " the chest," 

 protected behind by the back-bone and 

 shoulder-blades, in front by the arms, the 

 elastic gristle of the breast, and the rounded 

 ribs. Breadth of chest arises not from the 

 largeness of the lungs, but of the collar bone, 

 which separates the arms, just as a milk- 

 maid's yoke keeps apart her pails. The 

 horse has scarcely any collar-bone, because 

 his fore legs are used only for locomotion. 

 We pride ourselves on drawing in this part 

 of our form, just the part that should have 

 free play ; the lungs, the stomach, and the 

 liver, alone weighing four pounds. The 

 heart has two vessels, from one of which is 

 carried away the blue, impure blood; into 

 the other, the renovated fluid — renovated by 

 having come in contact with the oxygen of 

 the lungs — received, and thence again dis- 

 persed throughout the body. The condition 

 of the blood and of the health depends much 

 more upon the air breathed than even upon 

 the food received into the stomach. Diseases 

 of the lungs, the most common cause of 

 deaxh, arise chiefly from impurity of atmo- 

 sphere. It has been ascertained by a ma- 

 chine, on the principle of a gasometer, a 

 vessel rising, as inflated from a tube placed 

 in the mouth, on a scale carefully marked 

 and read off, that to every inch of stature a 

 man should possess eight cubic inches of 

 breath. As we make 75 pulsations in a 

 minute, each pulsation impelling 150 ounces 

 of blood, and requiring 20 cubic inches of 

 air to re-oxydize it, we may calculate that 

 we circulate 26 hogsheads of blood, and 

 require 36 hogsheads of air, every 24 hours. 



We spend more time in our bed-chamber 

 than in any other room, yet it is invariably 

 the worst room in the house, the narrowest, 

 lowest ; every avenue of air carefully closed 

 up, or if it does obtain entrance, usually 

 crossing the floor, so as to give one the 

 rheumatism in the legs, while the head is 

 half suffocated. Let there be a provision 

 near the ceiling for the admission of pure 

 air, such as that invented by Mr. Slier ing- 

 ham, the impure will certainly find its way 

 out. 



