302 THE BLOOD. [CHAP. XXVII. 



examining the capillary circulation in the transparent parts of some 

 animals, as the web of the frog's foot, they may be seen sparingly 

 at the margin of the current of red corpuscles, either stationary and 

 adherent to the wall of the blood-vessels, or slowly moving forward 

 in the layer of liquor sanguinis which is in contact with the wall, 

 and which is thus shewn to be comparatively motionless. 



The colourless corpuscles are much fewer in number than the 

 coloured ; it is said that they exist in the proportion of one colour- 

 less to fifty coloured, but that in inflammatory states of the blood, 

 the former are much more numerous, being as one in twelve. 

 After great loss of blood, the proportion of the colourless cor- 

 puscles is considerably increased. 



A very important inquiry is to determine 1 . The histological 

 relation of these particles to each other; and, 2. The part which 

 they take respectively in the vital phenomena of the blood. 



With regard to the first point, physiologists are divided in 

 opinion as to whether they may be regarded as distinct and in- 

 dependent particles, performing each their special functions, or 

 whether the one, namely, the colourless corpuscle, may be viewed 

 as an early or embryo condition of the red corpuscle. 



The weight of argument seems to favour the conclusion that the 

 colourless corpuscles are to be regarded as an early stage of the 

 Fig. i8o. coloured corpuscles, which 



are in the adult or perfect 



fa p, ~ state. In the earliest pc- 

 <5 riods of fetal life, the blood- 

 _ : corpuscles, as is shewn by 

 the researches of Vogt, Kol- 

 liker, and Cramer, originate, 

 in the same way as the ele- 

 ments of the tissues, from 

 nucleated cells, which are 

 the same in point of con- 

 stitution as the colourless 

 corpuscles; with this ex- 

 ception that they contain 



v Corpuscles from the blood vena of the cava hepatica of the , , , , , 



embryo chick on the twentieth day of incubation. A. Red between the IlUClCUS ailQ tllG 

 blood-corpuscles altered by water. B. Blood-corpuscles ,, . -. , , 



coherent and modified in shape by cohesion, c. , Large Cell, a Considerable number 

 spherical cells containing highly refracting granules (fatty); ., , , . , 



b, the same represented only in outline, to shew their OI grailUlCS, WlllCll ai'C 



shape; c, fully formed red corpuscles. Mag. 200 diam. , , . 



largest at the earliest pe- 

 riods of embryonic life. At later periods similar nucleated cells 



