208 



RED CORPUSCLES OF THE BLOOD. 



BED CORPUSCLES OP THE BLOOD. 



These are not spherical, as the name " globules," by which they were formerly 

 designated, would seem to imply, but flattened or disk-shaped. Those of the human 

 blood (fig. 239 and fig. 240, A) have a nearly circular outline, like a piece of coin, and 

 most of them also present a shallow cup-like depression or dimple on both surfaces ; 

 their usual figure is, therefore, that of biconcave disks. Their magnitude differs 

 somewhat even in the same drop of blood, and it has been variously assigned by 

 authors ; but the prevalent size may be stated at' -3^0^ f an i nc ^ (' 07 to ' 08 

 millimeter) 1 in diameter, and about one-fourth of that in thickness. A few 

 corpuscles may usually be found which are not more than about one- half this size 

 (microcytes), and others which are rather larger (up to about -g-oVo^ f an mcn )> and 



Fig. 239. HUMAN BLOOD AS SEEN ON THE WARM 

 STAGE. MAGNIFIED ABOUT 1000 DIAMETERS. 

 (E. A. S.) 



r, r, single red corpuscles seen lying flat ; r', r', 

 red corpuscles on their edge and viewed in profile ; 

 r", red corpuscles arranged in rouleaux ; c, c, crenate 

 red corpuscles ; p, a finely granular pale corpuscle ; 

 g, a coarsely granular pale corpuscle. Both have 

 two or three distinct vacuoles, and were undergoing 

 changes of shape at the moment of observation ; in 

 g, a nucleus also is visible. 



every gradation in size between these two 

 extremes may be met with, but the great 

 majority average -r-roi^h f au i ncn under 

 normal conditions. In some diseases, 

 especially pernicious anemia, the relative 

 number of microcytes is greatly increased. 



In mammiferous animals generally, the red 

 corpuscles are shaped as in man, except in the 

 camel tribe, in which they have an elliptical 

 outline. In birds, reptiles, amphibia, and most fishes, they are oval disks with a central 

 elevation on both surfaces (fig. 240, B, and fig. 245, from the frog), the height and extent of 

 which, as well as the proportionate length and breadth of the oval, vary in different 

 instances, so that in some fishes the elliptical form is almost shortened into a circle. 



The size of the corpuscles differs greatly in the different classes of Vertebrata ; they are 

 largest in the Amphibia. Thus in the frog they are about i^th of an inch long and j^th 

 broad ; in Proteus anguineus, J^th of an inch long and ^th broad ; in Amphiuma tridactylum, 

 where they are largest, the red corpuscles are one-third larger than those of the Proteus. In 



birds they range in length from about 2ob s th to j^th of an inch. Amongst mammals the 

 elephant has the largest red blood-corpuscles (atboth of an inch) ; those of the dog average 

 g^th of an inch ; those of the sheep gg^th of an inch ; the goat was long supposed to have 

 the smallest (o^th of an inch), but Gulliver found them about half this size in the Meminna 

 and Napu deer. 



In observations upon the blood of different races of mankind, Richardson found no constant 

 difference, the average diameter of the red blood-corpuscle being g^jth of an inch. The 

 corpuscles of many mammals, and notably the dog among the common domestic animals, 

 approach so nearly in size to the human blood-corpuscles as to be indistinguishable from them. 



When viewed singly by transmitted light the coloured corpuscles do not appear 

 red, but merely of a reddish-yellow tinge, or yellowish-green in venous blood. It is 



1 The one-thousandth part of a millimeter is often known as a micro-millimeter or micron, and is 

 represented by the Greek letter /u. The diameter of a red blood corpuscle is then expressed as 7 8 

 microns 7ju-^8/u. 



