142 



ANATOMY FOR NURSES 



[Chap. IX 



(1) It carries to the tissues water and the nutritive substances 

 resulting from digestion. These are required by each individual 

 cell in order to enable it to carry on its metabolic processes. 



(2) It carries to the tissues oxygen, absorbed from the air 

 in the lungs. Every individual cell requires oxygen, in order to 

 provide heat and energy. 



(3) It carries from the tissues various waste ])roducts. These 

 are not only useless, but poisonous, and must be eliminated by the 

 lungs, kidneys, and skin. 



(4) It serves as a medium for the transmission of certain 

 secretions. The presence of these secretions promotes oxidation 

 and metabolism. 



(5) It aids in equalizing the temi)erature of the body. Blood 

 passing through a tissue which is undergoing lively metabolism 

 will have a higher temperature when it leaves than it had when it 

 entered. This extra temperature will be lost in passing through 

 a tissue that is not so active. In this way an average temperature 

 is maintained. 



(()) It aids in protecting the body from infections. 



Composition of the blood. — Seen with the naked eye, the 

 blood appears opaque and homogeneous ; but when examined 

 with a microscope it is seen to consist of minute, solid particles 

 called corpuscles, floating in a transparent, slightly yellowish fluid 

 called plasma. 



Red or erj'throcytes. 

 Corpuscles \ White or leucocjrtes. 

 Blood plates. 

 Water, £0 %. 

 Blood { Proteins. 



Extractives. 

 Inorganic salts. 

 Gases. 

 Enzj'^mes. 

 Internal secretions. 

 Immune bodies. 



Red corpuscles. — The red corpuscles are circular biconcave 

 disks, with rounded edges. The average size is s^^-q of an inch 

 (0.008 mm.) in diameter, and about 12^0^ (0.002 mm.) of an inch 

 in thickness. Because of their extremely small size, the red cor- 

 puscles do not appear red when viewed singly with a microscope, 



Plasma 



