80 ANATOMY FOR NURSES. [CHAP. VII. 



To sum up briefly, the blood is composed of 



Proteid substances. 



Fats. 

 PLASMA , 



Extractives. 



Salts. 

 rRed 

 CORPUSCLES j and 



I 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 

 carbonic acid and urea, which, in accumulating, 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. 



