RED CORPUSCLES OF THE BLOOD. 379 



himself and of a few other persons a small number, varying 

 with the period of the day, of minute bodies, differing from the 

 ordinary corpuscles in their spheroidal form and in some other 

 peculiarities, together with transitional forms between them 

 and the ordinary corpuscles. Further, in accordance with the 

 frequently cited observation, though standing much in need of 

 confirmation, of Lehmann,* the blood of the hepatic vein con- 

 tains corpuscles of smaller size and more spheroidal form than 

 usual, whilst those of the portal vein are of the ordinary kind. 



The surface of the common form of corpuscle appears smooth, 

 and the substance of the disk exhibits in its interior no indi- 

 cation of any difference in the index of refraction of its several 

 parts. In passing from the centre to the circumference, however, 

 there is a distinct change in the colour and transparency. 

 In that position of the corpuscle in which the disk appears 

 broadest and its edge most sharply defined, the centre is trans- 

 parent, and the lateral portions are darker, whilst the extreme 

 edge again presents a clearer ring. The latter is occasioned by 

 the refraction which transmitted light experiences in the focal 

 plane of the microscope when it traverses objects bounded by 

 circular contours.-)- 



The appearance presented by human blood corpuscles is dif- 



Fig. 68. 



ferent from that of the corpuscles of animals with elliptical 

 corpuscles. External to the elliptical border of the flat surface 

 of the disk there may be observed, at least in Birds, Amphibia. 



* Physiologische Chemie, Band ii., pp. 85 and 232. 



t Nageli and Schwendener, Das Mikroskop, Theil i., p. 184, et seq. 

 Harting, Das Mikroskop. Braunschweig, 1866, Band ii., p. 26, et seq. 



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