ITS DIFFERENT PHASES OF DEVELOPMENT IN THE ANIMAL SERIES. 
71 
exist then, but in embryos a little further advanced than that, the blood of which is 
at present under consideration, I found the number of small red corpuscles greater, 
— that of the nucleated red corpuscles less ; and in foetuses still farther advanced, the 
well-marked nucleated red corpuscles had altogether given place to the small red 
corpuscles. 
52. Putting the small red corpuscles out of view, the blood of the early mammiferous 
embryo here examined resembles the blood of the oviparous Vertebrata in presenting, 
besides granule-cells, nucleated cells both in uncoloured and coloured stages. 
53. In regard to the red nucleated cells it is to be remarked, that the circular ones 
were the most numerous, and as they are identical in appearance, size and structure, 
with the red corpuscles of the blood of the Lamprey, with the exception that their 
cellseform nuclei are larger, the blood of the mammiferous embryo might be com- 
pared to a mixture of the blood of the Lamprey, with a small quantity from a skate 
or frog to supply the few oval red nucleated cells, and a small quantity from a calf to 
supply the small red corpuscles. 
54. I now proceed to examine the corpuscles of the fully-formed blood of Man and 
the Maminifera, and to compare them with those of the blood of the early mammi- 
ferous embryo and of oviparous vertebrate animals. 
Examination of the Corpuscles of the fully -formed Blood of Man and the Mammifera , 
and a comparison of them with those of the Blood of the early Mammiferous Embryo 
and of Oviparous Vertebrate Animals. 
55. In this examination and comparison, I will inquire, — first, if there be any cor- 
puscles corresponding to granule-cells ; secondly, if any corresponding to nucleated 
cells ; and lastly, if the “ red corpuscles” are found not to correspond to nucleated 
cells in the coloured stage, I will inquire into what they correspond to. 
56. Here I omit, as I did above in the case of the blood-corpuscles of the Frog, the 
use of the terms “lymph” and “colourless” corpuscles as altogether destitute of 
definite meaning, purposing in the second part of this paper to consider, likewise 
in the case of Man and the Mammifera, what relationship exists between the corpus- 
cles of their blood, usually confounded together under these names, and the corpus- 
cles of their lymph. 
57- Granule Blood-cells. — The corpuscles in the blood of Man and the Mammifera 
corresponding to the granule-cells of the blood of the animals above considered, are 
certain of those commonly spoken of under the name of “lymph” or “colourless” 
corpuscles— not all, as will be shown below, par. 66. 
58. Both coarsely and finely granular stages of the granule-cell may be recog- 
nised. In human blood they in general become speedily collapsed after the blood is 
drawn, and some, especially those in the finely granular stage, may be seen on careful 
inspection shooting out processes (fig. 2 a.) like the same cells in the blood of the 
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