PROFESSOR TURNER ON THE PLACENTATION OF THE SLOTHS. 81 
I have already stated that differences in the degree of injection of the 
maternal vessels existed in different parts of the placenta. When the animal 
had died, its placental vessels were filled with blood, and when the injection 
was passed into the uterine arteries and veins, it had in many places entirely 
filled the lumen of the vessels, and in others it was intermingled with the blood 
corpuscles ; but in various parts of the organ, where the injection had not pene- 
trated, the serpentine and convoluted maternal vessels were occupied only by 
the blood-corpuscles. In some instances the corpuscles were so closely packed 
together as completely to fill the lumen of the vessel; in others they had 
shrunk into the centre of the vessel, so as to leave a space between them and 
the wall, which latter was in such instances clearly defined. And I may state 
that, as soon as the eye became familiar with the characters of these serpentine 
maternal vessels, their appearance and arrangement could be studied in those parts 
of the placenta, where they were filled only with blood-corpuscles, equally well as 
where they had been more or less perfectly distended with the coloured injection. 
The characters presented by the red blood-corpuscles are worthy of con- 
sideration. They had the well-known circular form of the mammalian blood- 
disc, and the greater number were non-nucleated. But amongst them was a 
proportion of corpuscles in which the central part, differentiated from the 
peripheral portion of the corpuscle, was bounded by a sharp line, so as to give 
the appearance of a central nucleus. It should be stated that, before this 
observation was made, the placenta had been injected and hardened in spirit ; 
but if the nucleated appearance had been occasioned artificially, it is probable 
that a greater proportion, or even the whole of the red corpuscles, would have 
been similarly affected. On the whole, then, I am disposed to think that the 
“nuclei” are normal and not artificial productions in a proportion of the red 
blood-dises of this animal. And here I may point out that previous observers 
have referred to the presence of nucleated red blood-corpuscles in other 
species of Tardigrada. KtuHneE remarks, that amongst the mammalia, only 
individuals (Camels, Tardigrades) possess nucleated blood-corpuscles.* Dr 
ROLLESTON statest that Mr Mosetey called his attention to the appearance of 
nucleation in dried blood-corpuscles of Cholepus didactylus. Further observa- 
tions satisfied them that although a certain number of the dried blood-corpuscles 
of this sloth do contain one or more nuclei irregularly and eccentrically placed, 
the immense majority possess the usual mammalian non-nucleated character. 
Mr GULLIVER, in commenting { on these observations, says, that as the nuclei 
were not subjected to chemical examination, their real character is doubtful. 
But even if these nuclei are real structures, the small proportion of corpuscles 
* Lehrbuch der physiologischen Chemie. Leipzig, 1868, p. 195. 
+ Quart. Journal of Microscopic Science, vii. p. 127. 
{ Journal of Anatomy and Physiology, ii. p. 1. 
