102 ANATOMY FOB, NURSES. [CHAP. VIII. 



sues take up from the blood and give up to the blood different 

 things at different rates and at different times, but all the 

 tissues take up oxygen and give up carbon dioxide in varying 

 quantities. From this it follows, on the one hand, that the 

 composition and character of the blood must be forever varying 

 in different parts of the body ; and, on the other hand, that the 

 united action of all the tissues must tend to establish and main- 

 tain an average uniform composition of the whole mass of blood. 

 To sum up briefly, the blood is composed of 



Proteid substances. 



, Fats. 

 PLASMA i . 



Jkxtractives. 



CORPUSCLES 



Salts. 

 Ked 

 and 

 White. 



The plasma is chiefly the carrier of nutriment to the tissues, 

 and of waste matter from the tissues. The red corpuscles are 

 pre-eminently the carriers of oxygen ; the white corpuscles may 

 be regarded as scavengers, as important protective elements in 

 many diseases, and possibly as contributors to the construction 

 of new tissue where such has been injured or destroyed. 



NOTE. When we remember that the tissues live on the blood, we recognize 

 the gravity of those diseased conditions in which important elements are being 

 constantly drained away from the blood, as, for example, the albumin in dis- 

 eases of the kidneys, the red corpuscles in hemorrhage, the water of the blood 

 in cholera, etc. Withdrawal of oxygen, as we all know, causes instant death, 

 and a constant supply of fresh air is a vital necessity of life. Nor is it of less 

 importance that the blood be kept free from those waste matters, pre-eminently 

 carbon dioxide and urea, which, in acciimulating, poison the system, and, if 

 not excreted in sufficient amount, will as surely cause death as the withdrawal 

 from the blood of any of its most vital constituents. 



