298 THE BLOOD. [CHAP. XXVII. 



any other part (Fig. 173). Its size varies considerably : in the 

 same drop of blood there are corpuscles of all sizes within a range 

 of from ^Vo to T gVo f an " lcn i* 1 diameter, the average being 

 from the -3jVo to 3^0- With a good microscope, and a magnify- 

 ing power of 200 diameters, the characters of the blood-corpuscles 

 Fig. 173. may be most clearly seen, and when 



the instrument is perfectly adjusted, 

 the double concave surface may be 

 unequivocally demonstrated. If the 

 corpuscles are floated in water, they 

 become biconvex : if in a fluid 

 denser than serum, as in a strong 

 saline or saccharine solution, they 



Red corpuscles from human blood:-. J P ut On a shrivelled aspect, 



and become lated on their 



a roii. Magnified 400 times. surface (Fig. 174, B) ; this shrivelled 



appearance may again be got rid of by diluting the menstruum 

 and reducing its specific gravity to the lowest point. 



Fig , 174 . It has been affirmed, by Mulder 



* ^ an ^ ^ ers ' ^at * ne blood-corpuscles 

 ** f venous blood are biconvex 

 I <f those of arterial being biconcave 

 ^ and they attribute the difference 



of colour of these two kinds of blood 

 to the different mode in which the 

 light is reflected from the concave 

 an <* the convex surfaces of their 



altered by amenstruum of high density. respective Corpuscles. With refer- 



ence to this doctrine, we have only to state that we have care- 

 fully examined two portions of the same blood after they had been 

 agitated in oxygen and carbonic acid gas, and thus been rendered 

 respectively scarlet and purple, but that we have failed to detect 

 any well-marked difference in shape between the blood corpuscles 

 of the two specimens. 



The blood-particles have a remarkable tendency to aggregate in 

 rolls like pieces of coin (Fig. 173, b) : this tendency, as has been 

 already remarked, is said by some to be greatly increased in blood 

 which forms a buffy coat in its coagulation. 



The red blood-corpuscle of Mammals resembles in shape and structure that 

 of man (Fig. 174) : there is much diversity of size in the various orders ; it is 

 smallest in the ruminants, and the smallest known is that of the Napu musk- 

 deer, which is reported by Mr. Gulliver not to exceed ^th of an inch in diameter. 



