403. . DR THOMAS H. BRYCE ON 
Besides the erythrocyte series, there is a large leucocyte contingent in the spleen. 
The fully unfolded leucocytes are of two main classes. 1st, Small cells, with horse- 
shoe or lobed nuclei, with rather closely packed chromatin nucleoli, and a small cell body 
composed of hyaline blue-staining protoplasm, though sometimes it contains granules. 
2nd, Large cells, with polymorphic nuclei and a large cell body, im which the centro- 
some is always surrounded by a well-developed radial sphere and aster. The proto- 
plasm is either hyaline and blue-staining or granular, and the granulation is either fine 
or coarse. The fine granules stain in some cells blue, in others red, and the coarse 
granulation of the eosinophile cells is not always of the same size. 
Compared to the erythroblasts, the leucocytes are in relatively small numbers, but 
in the spaces and sinuses there are many of the cells which have all the characteristics 
of leucoblasts (fig. 33, Pl. IV.). The nuclei vary in size, but generally speaking are 
smaller than those of the largest spleen cells (18 » against about 24 «), but have 
otherwise the same character and reaction. 
The protoplasm is reduced to a very narrow zone, is hyaline, and stains pure blue. 
Many nuclei are deeply notched (fig. 33, Pl. IV.), as if beginning to undergo poly- 
morphic metamorphosis. 
As leucocytes in all varieties are abundant in every tissue of the body, and 
especially round the kidney tubules and gut, as I shall presently describe, it is much 
less certain whether they are actually formed in the spleen at this stage than that the 
erythroblasts are rising there. 
The great difficulty is, that it is impossible to distinguish a leucoblast from a 
primitive spleen cell. We have here repeated the same problem dealt with before in 
connection with the origin of the two classes of corpuscles from the mesenchyme cells; 
and considering that the spleen is merely a tract of mesenchyme, which may be ~ 
supposed to retain its primitive potential characters, the same general scheme may not 
unreasonably be considered to apply, which would derive from the primitive cells of 
the rudiment both classes of corpuscles by specialisation along different lines. My 
observations on the spleen are thus in strict accord with those of LacuussE* in his 
classical work. My large mononuclear cell takes the place of his noyau d’origine, a 
term borrowed from Poucuer,*+ who first formulated the general scheme here adopted 
from his work on the blood of Triton. 
The leucocytes, in their several varieties, are found in the blood-vessels and scattered 
in every tissue, but are specially crowded in the wall of the gut in the mesentery and in 
the tissue surrounding the tubules of the kidney. 
Pseudo-lymphoid Tissue of Kidney. 
The tract described at stage 32 has disappeared in front with the atrophy of the 
pronephros, but it can be identified in the region of the kidney, and the general 
* Loe. lt. t+ Gaz. Méd. de Paris, 1879. 
