384 THE BLOOD, BY ALEXANDER ROLLETT. 



millimeter of blood, in which about from 2,000 to 3,000 cor- 

 puscles were counted in the space of an hour. 



Comparative enumerations, with test specimens of blood 

 diluted to various extents, and measured in capillary tubes of 

 various widths, gave a difference of two to three per cent, in 

 the numbers, and seldom amounted to five per cent. 



In a cubic millimeter of the healthy blood of a man, 

 5,000,000 red blood corpuscles were estimated to be present. 



From this, and from the above-stated dimensions respecting 

 the volume and surface of the corpuscles, there appear to be in 

 a hundred volumes of blood thirty-six volumes of corpuscles and 

 sixty-four volumes of plasma. The surface of the corpuscles in 

 one cubic millimeter may be estimated to amount to 643 square 

 millimeters. 



Vierordt, Welcker, and Stolzing have also counted the blood 

 corpuscles of various animals. 



ALTERATIONS OF THE RED BLOOD CORPUSCLES. 



We shall now pursue another line of inquiry. Up to the pre- 

 sent time, independently of the above-given enumerations, we 

 have, as far as possible, considered the blood corpuscles in their 

 normal condition. We are, however, indebted for much im- 

 portant information to the observation of certain changes 

 which the corpuscles undergo under various circumstances, as 

 well as to the results obtained from experimental histology. 



For the purposes of inquiry into the nature of the red cor- 

 puscles, mechanical agents, the discharge of the Leyden flask, 

 the application of induced and constant currents, exposure to 

 heat and cold, and lastly, the addition of various chemical 

 agents have been employed. 



1. In freshly prepared specimens of human blood it may fre- 

 quently be seen, after the lapse of a variable space of time, that 

 the borders and surfaces of the corpuscles have lost their 

 smooth aspect. The borders appear dentated ; the surfaces, as 

 may best be seen when the corpuscles are rolling over, are 

 beset with little eminences. At the same time the corpuscles 

 become smaller and more spherical (fig. 69). A few such cor- 

 puscles are often visible in fresh blood, immediately after it has 



