BLOOD 
449 
the most deadly of our diseases, but through the use of the 
diphtheria antitoxin the danger has been greatly reduced. 
Bronchitis and pneumonia are germ diseases located in the 
bronchial tubes of the lungs. Pneumonia is a frequent 
cause of death among aged people. 
Tuberculosis of the throat and lungs is a widely distributed 
disease which causes many deaths each year. See page 489. 
Adenoids are the result of an enlargement of the pharyn¬ 
geal tonsil. The commonest result is the stopping of the 
nasal passage. Almost all mouth¬ 
breathing children have adenoids. 
These should be removed not only be¬ 
cause they prevent the natural use of 
the nasal passage but because they 
often cause deafness. 
355. Blood. — The blood is the fluid 
which circulates through the heart, 
arteries, and veins, supplying nutritive 
material to all parts of the body. 
Blood is made up of a fluid (plasma) 
which contains cells or corpuscles 
(Latin, corpusculum, little body). The 
blood cells or corpuscles are of two 
kinds, red and white. 
The red corpuscles are colored with a substance called 
hcemoglobin (he-mo-glo'bm: Greek, haima, blood; globus, 
ball). When a few of these corpuscles are examined through 
a microscope, they appear yellowish instead of red ; but when 
a large number of them are seen in a mass, the red color is 
apparent. When the red cells are first formed, they have a 
nucleus which gradually disappears. As a result, the mature 
red corpuscles, unlike all the other cells we have studied thus 
far, have no nucleus. Red corpuscles are about 3 aVo 1 an 
inch in diameter and t^too °f an i n °h thick. 
The red corpuscles carry oxygen from the lungs to the 
Figure 398 . — Photomi¬ 
crograph of Blood of 
Frog. 
The minute black spot 
in each corpuscle is the 
nucleus. The nucleus is 
absent in human red blood 
corpuscles. 
