THE BLOOD. 



79 



The general conclusions to be drawn from these observations have 

 m summed up as follows by Prof. Ray Lankester: 

 "The red bipod-corpuscle of the vertebrata is a viscid, and at the same 

 :ime elastic disc, oval or round in outline, its surface being differentiated 

 mewhat from the underlying material, and forming a pellicle or mem- 

 mine of great tenuity, not distinguishable with the highest powers 

 whilst the corpuscle is normal and living), and having no pronounced inner 

 limitation. The viscid mass consists of (or rather yields, since the state 

 >f combination of the components is not known) a variety of albuminoid 

 ind other bodies, the most easily separable of which is haemoglobin; sec- 

 mUy* the matter which segregates to form Roberts'^ macula; and thirdly, 

 residuary stroma, apparently homogeneous in the mammalia (excepting 

 far as the outer surface or pellicle may be of a different chemical 

 lature), but containing in the other vertebrata a sharply definable 

 lucleus, this nucleus being already differentiated, but not sharply deline- 

 bed during life, and consisting of, or separable into, at least two com- 

 ments, one (paraglobulin) precipitable by carbon dioxide, and remov- 

 ible by the action of weak ammonia; the other pellucid, and not gran- 

 dated by acids." 



The White or Colorless Corpuscles. In human olood the white 

 >r colorless corpuscles or leucocytes are nearly spherical masses of 

 inular protoplasm without cell wall. The granular appearance, more 

 larked in some than in others (vide infra), is due to the presence of par- 

 :icles probably of a fatty nature. In all cases one or more nuclei exist in 

 )h corpuscle. The size of the corpuscle averages ^--g- of an inch in 

 liameter. 



In health, the proportion of white to red corpuscles, which, taking 

 average, is about 1 to 500 or 600, varies considerably even in the 

 mrse of the same day. The variations appear to depend chiefly on the 

 imouut and probably also on the kind A B 



)f food taken; the number of leuco- 

 3ytes being very considerably increased 

 iy a meal, and diminished again on 

 sting. Also in young persons, dur- 

 ing pregnancy, and after great loss 

 )f blood, there is a larger proportion 

 )f colorless blood-corpuscles, which 

 probably shows that they are more rapidly formed under these circum- 

 stances. In old age, on the other hand, their proportion is diminished. 



Varieties. The colorless corpuscles present greater diversities of 

 form than the red ones do. Two chief varieties are to be seen in human 

 blood; one which contains a considerable number of granules, and the 

 other which is paler and less granular. In size the variations are great, 

 for in most specimens of blood it is possible to make out, in addition to 



FIG. 77. A. Three colored blood-corpuscles. 

 B. Three colorless blood-corpuscles acted on 

 by acetic acid; the nuclei are very clearly 

 visible. X 900. 



