70 ON THE BLOOD-CORPUSCLES OF THE TWO-TOED SLOTH. 



Since writing the above, I have, through the kindness of T. J. 

 Moore, Esq., of the Liverpool Museum, had the opportunity of ex- 

 amining the blood of an elephant, Elephas Indicus, which had died 

 a week previously in Mr. Mander's Menagerie. 



In this blood very many nucleated red blood-cells were visible ; but 

 in all observed, with perhaps one exception, the coloured factor was 

 internally placed, whilst the colourless formed the envelope. It is, of 

 course, impossible to explain this arrangement as being a retention 

 in a mammal of the condition usually met with in ovipara ; for in 

 these latter creatures it is the nucleus which is colourless, whilst 

 the parts exteriorly to it are coloured. When the elephant's blood- 

 cells turned over in the slide, they presented much the appear- 

 ance which a figure of a blastodermic vesicle does when its area 

 pettucida is dumb-bell shaped, the envelope holding, in many cases, 

 almost as favourable a relation in point of size to the nucleus, if so 

 it may be called, as the blastodermic vesicle does to its area pellucida. 

 This appearance I have noted also in the blood of the horse, of the 

 rabbit, and of the human subject. It is different enough from that 

 described by Dr. Roberts in the Royal Society's ' Proceedings,' 

 March 19th, 1863, as produced in mammalian blood-cells by the 

 action of tannin ; but, on repeating his experiment, I satisfied my- 

 self that the two sets of cases had this in common, viz. that they 

 show that the homogeneous coloured mammalian blood-cells may be 

 separated into two parts — one colourless and the other coloured — 

 of which the latter shall occupy the smaller area. 



I am inclined to think that the elephant's blood, though not 

 fresh, still gave better opportunities for judging of the real nature 

 of the appearance of nucleation than dried slides, such as those of 

 the sloth's corpuscles, could give. 



[Note.— The Editor may refer to some observations on the blood of Cholopus hoff- 

 manni (Trans. Koy. Soc. Edinb. xxvii. p. 81), in which he describes, in a proportion 

 of the corpuscles, the central part differentiated from the peripheral part of the cor- 

 puscle by a sharp line, so as to give the appearance of a central nucleus.] 



