146 



THE CIRCULATION 



with a needle. The total quantity of blood in the body is 

 estimated at about one-eighth of its weight, or eighteen pounds. 



3. The color of the blood, in man and the higher animals, 

 as is well known, is red; but it varies from a bright scarlet 

 to a dark purple, according to the part whence it is taken. 

 " Blood is thicker than water," as the adage truly states, and 

 has a glutinous quality. It has a faint odor, resembling that 

 peculiar to the animal from which it is taken. 



4. When examined under the microscope, the blood no 

 longer appears a simple fluid, and its color is no longer red. 

 It is then seen to be made up of two distinct parts : first, a 

 clear, colorless fluid, called the plasma; and, secondly, of a mul- 

 titude of minute solid bodies, or corpuscles, that float in the 

 watery plasma. The plasma, or nutritive liquid, is composed 

 of water richly, charged with materials derived from the food, 

 viz., albumen, which gives it smoothness ; fibrin ; certain fats ; 

 traces of sugar ; and various salts. 



5. The Blood Corpuscles. In man, these remarkable "little 

 bodies," as the meaning of the word corpuscles signifies, are of 



a yellow color, but by their vast 

 numbers impart a red hue to the 

 blood. They are very small, hav- 

 ing a diameter of about ^Vo" of an 

 inch, and being one-fourth of that 

 fraction in thickness; so that if 

 3500 of them were placed in line, 

 side by side, they would only ex- 

 tend one inch; or, if piled one 

 above another, it would take at 

 FIG. 33. THE BLOOD CORPUSCLES, least 14,000 of them to stand an 



HIGHLY MAGNIFIED ^^ J^ga. AlthOUgh SO SHiall HI 



size they are very regular in form. As seen under the micro- 

 scope, they are not globular or spherical, but flat, circular, and 

 disc-like, with central depressions on each side, somewhat like 



8. Color of blood ? Its consistence ? Odor ? 



4. What is stated of the blood as viewed under the microscope ? 



5. State what you can of the little bodies called corpuscles. 



