Physiology and Hygiene for Secondary Schools

is the blood able to take it up at the lungs and give it off at the cells? What becomes of it after be

e to combine with most of the other elements to form chemical compounds. A familiar example of its combining action is found in ordinary combustion, or burning. On account of the part it plays in this process, oxygen is called the supporter of combustion; but it support

ree, or uncombined, condition-the for

of compounds, such as the co

when it is passing from the free state into one of combination. It is separated from its compounds and broug

oms that are called molecules. In an element the molecules are made up of one kind of atoms, but in a compound the molecules are made up of as many kinds of atoms as there are elements in the compound. Changes in the composition of substances (called chem

oms of carbon unite, forming molecules of the compound known as carbon dioxide. The chemical formula of this compound, which is CO_2, shows the proportion in which the atoms unite-one atom of carbon

les of slow oxidation are found in certain kinds of decay and in the rusting of iron. Combustion is an example of rapid oxidation. Slow and rapid oxidation, while differing widely in their

own by the constancy of the body weight. Nearly two pounds of oxygen per day are known to enter the cells of the average-sized person. If this became a permanent part of the cells, the body would increase in weight from day to day. Since the body weight remains constant, or

t it is possible for oxygen to serve a purpose and at the same time pass on through[pg 107] the place where it serves that purpose, is seen by studying the combustion in an ordinary stove (Fig. 5

ve illustrating

r forms of energy,45 including motion. It is the purpose of oxygen to keep up these oxidations and, by so doing, to aid in supplying the body with energy. It ser

y of oxygen to unite with substances and the well-known fact that oxygen is an important natural agent in purifying water. It seems probable, therefore, that it may to a slight extent serve this purpose in the body. It is probable also that oxygen aids thro

misleading, for oxygen has no more to do with the maintenance of life than have the food materials with which it unites. Life appears to be more dependent upon oxygen than upon food, simply because the supply of it in the body at any time is exceedingly small. Being continually surrounded by an atmosphere containing free ox

us movement through the body is a necessity. The oxygen compounds must be removed as fast as formed in order to make room for more free oxygen. This movement has already been studied in connect

cells, the oxygen passes twice through the blood-once as it goes toward t

ates the oxygen when it reaches the capillaries in the tissues. The separation of the oxygen from the hemoglobin at the tissues appears to be due to two causes: first, to the weakness of the ch

oxygen pressure is less than one half pound to the square inch. The oxygen pressure at the lungs, which amounts to nearly three pounds to the square inch, easily causes the oxygen and the hemoglobin to unite, while the almost complete absence of any oxygen pressure at the tiss

n dioxide (CO2), water (H2O), and urea (N2H4CO). The first is formed by the union of oxygen with carbon, the second by its union with hydrogen, and the third by its union with nitrogen, hydrogen, and carbon. These compounds are carried by the blood to the o

ide through the body (S.D. Magers). Each moves from a place of r

ugh the blood is accounted for in the same[pg 111] way as the passage of the oxygen. Its ability to dissolve in liquids and to enter into chemical combination varies as the carbon dioxide pressure47 This in turn varies with the amount

carbon dioxide, illustrating the difference

he contrary is used to some extent to extinguish fires. It is formed by the oxidation of carbon in the body, and by the combustion of carbon outside of the body. It is also formed by the decay of animal and veg

his tendency is counteracted through the agency of vegetation. Green plants absorb the carbon dioxide from the air, decompose it, build the carbon into compounds (starch, etc.) that become a part of the plant, and return the free oxygen to the air (Fig. 57). In doing this, they not

anium leaf showing breathing p

oxygen leaves the body as a part of the waste compounds which it helps to form. The free oxygen is transported from the lungs to the cells by means of the hemoglobin of the red corpuscles, while the combined

ies of oxygen. How does it unite with othe

in the body. What properties en

nently in the body? How does the oxygen entering the b

us introduction of oxygen into the body,

up and give off oxygen? How is the plasma a

cent of this is carbon dioxide, calculate the number of cubic feet of the gas expell

volume of carbon dioxide, if o

at carbon, the ratio by weight of carbon to oxy

sposition of carbon dio

TICA

nd heat strongly in a gas or alcohol flame. The crystals first melt, and the liquid which they form soon appears to boil. If a splinter, having a spark on the end, is now inserted in the tube, it is kindled into a flame. This show

table. Fill four large-mouthed bottles with water and, by covering with cardboard, invert each in the trough of water. Arrange the test tube conveniently for heating, letting the end of the glass tube terminate under the mouth of one of the bottles (Fig. 58). Using an alcohol lamp or a Bunsen burner, heat over the greater portion of the tube at first, but gradually concentrate the flame upon th

atus for gene

the bottle and observe the change in the rate of burning. The air contains free oxygen, but it is diluted wi

indles the spark into a flame, withdraw from the bottle and blow out the flame, but again insert the spark. Repeat the experiment

r in the flame of an alcohol lamp or Bunsen burner, and lower it into a bottle of oxygen. Observe the change in the rate of burning, the color of the flame, and

nite the melted sulphur which adheres, and insert it quickly in a bottle of oxygen. Observe the dark, brittle material which is

e. Ignite the charcoal in a hot flame and lower it into a vessel of oxygen. Observe its combustion, letting it remain in the bottle until it c

rdboard, and bring the gas and the limewater in contact by shaking. Note any change in

r, keeping the top covered. Add limewater

half a gallon. Barely cover the marble with water, and then add hydroc

it poss

splinter to see if it

immediately, and if a spark remains on the splinter, thrust it into the bottle of oxygen. Then insert the relighted splinter into the carbon dioxide. Repeat several times, kin

water, though not far enough to spill the acid, and[pg 116] then insert a burning splin

for illustrating passage

101) showing the presence of

le in this stopper, but terminating near the top of the bottle, and to this is connected a rubber tube about eighteen inches in length. The arrangement is now such that by sucking air from the top of the bottle, it is made to enter at the distant end of the tube containing the charcoal. After filling the bottle one third full of limewater, heat the tube containing the charcoal until it begins to glow. Then suck t

g