HISTOLOGY OP THE RED BLOOD-CORPUSCLES. 7 



finger, and then blown into the solution. The two fluids are well mixed by 

 rotating the stirrer between the thumb and finger, and a small drop of this dilution 

 is placed in the centre of the cell, the covering glass gently put upon the cell, and 

 secured by the two springs, and the plate placed upon the stage of the microscope. 

 The lens is then focussed for the squares. lu a few minutes the corpuscles have 

 sunk to the bottom of the cell, and are seen at rest on the squares. The number 

 in ten squares is then counted, and this, multiplied by 10,000, gives the number 

 in a cubic millimetre of blood. " 



Welcker attempted to ascertain the number of corpuscles by estimating the 

 colouring-power of the blood. His method was not exact, but other observers 

 have constructed apparatus for determining the amount of haemoglobin. 



(.) Ked blood-corpuscles are characterised by their great ELASTICITY, 

 FLEXIBILITY, and SOFTNESS. [The elastic property is shown by the 

 great extent to which red corpuscles still within the circulation may be 

 distorted, and yet resume their original form as soon as the pressure 

 is removed.] 



3. Histology of the Human Red Blood-Corpuscles. 



Wheu observed singly, blood-corpuscles have a yellow colour with 

 a slight tinge of green ; they seem to be devoid of an envelope, are 

 certainly non-nucleated, and appear to be homogeneous throughout. 

 Each corpuscle consists (1.) of a framework, an exceedingly pale, trans- 

 parent, soft protoplasm the stroma (Kollett) ; and (2.) of the red 

 pigment, or haemoglobin, which impregnates the stroma, much as 

 fluid passes into and is retained in the interstices of a bath-sponge. 

 Some observers (Bottcher, Eberhardt, Strieker), maintain that the 

 corpuscles contain a nucleus, but this is certainly a mistake. 



4. Effects of Reagents. 



(A.) Vital Phenomena. Blood-corpuscles contained in shed blood 

 or even in defibriiiated blood, when it is reintroduced into the circula- 

 tion retain their vitality and functions undiminished. Heat acts 

 powerfully on their vitality, for if blood be heated to 52C., the 

 vitality of the red corpuscles is extinguished. Mammalian blood may 

 be kept for four or live days in a vessel under iced water, and still 

 retain its functions ; but if it be kept longer, and reintroduced into 

 the circulation, the corpuscles rapidly break up a proof that they 

 have lost their vitality (Laudois). Blood freshly shed from an artery, 

 frequently shows a transformation of the corpuscles into a peculiar 

 mulberry-shape. [This is the so-called crenation of the coloured cor- 

 puscles. It is produced by poisoning with Calabar bean (T. E. Fraser), 

 and also by the addition of a 2 per cent, solution of common salt]. The 



