86 The Functions of the Blood. 



THE FUNCTIONS OF THE BLOOD. 



BY C. W. HEATON, 

 Professor of Chemistry to Charing Cross Hospital College. 



Every one who has looked through a microscope at a drop of 

 blood, knows that the red or purple colour is confined to 

 certain minute discs, which resemble pieces of money in form, 

 and which float in a clear yellow liquid. The discs are known 

 to physiologists as the blood-corpuscles, and the liquid as liquor - 

 sanguinis. Both these constituents of the blood have their 

 own specific functions to fulfil in the operations of life, and 

 both have been the subject of numberless researches. Very 

 much still remains to be done ; but it is not too much to as- 

 sert that this most wonderful of liquids is slowly yielding up 

 its secrets to the patient workers who have so long sought for 

 them in vain, and that ' ' the blood, which is the life " of the 

 animal, is no longer the utter, hopeless mystery which it has 

 for ages remained. 



Careful microscopic measurements have been made of the 

 size of the corpuscles in the blood of different animals, and it 

 is now generally agreed that in the human subject their 

 average length is } -3200th of an inch, and their thickness 

 l-12400th of an inch. Hence it would be possible, if they 

 were packed close together, for 8,126,464 to lie in the compass 

 of one cubic millimetre — a space not larger than a good-sized 

 pin's head. Now the corpuscles occupy, in the aggregate, 

 about one half of the volume of the blood,* and we are, there- 

 fore, able to form a good guess at their probable number. 

 Vierordt and "Welker have, indeed, gone through the laborious 

 process of counting them ; and the former fixes their number 

 at 5,069,000, and the latter at 4,600,000, in the cubic milli- 

 metre. It will be seen that these figures agree tolerably well 

 with the rough calculation founded on the size of the corpuscles, 

 and we are, therefore, forced to admit that the tiny red drop 

 obtained from the finger by the prick of a needle, may contain 

 four or five millions of these curious bodies. Such figures, 

 however, give but vague ideas to the mind. A more distinct 

 one is, perhaps, conveyed in the fact, that a room sixty feet 

 long, thirty feet wide, and fifteen feet high, could not contain 

 as many grains of corn as there arc corpuscles in a single tea- 

 spoonful of human blood, the number being, approximately, 

 eighteen thousand millions ! 



* This is, of course, only a rough approximation. Their quantity varies 

 extremely in ditl'erent parts of the body, and even at different times of the day. 



