288 DR A. J. WHITING ON THE 



that of a ring or hollow sphere. Some cells show many small, deeply stained nuclei, 

 together with a few larger, faintly stained vesicular nuclei. Occasionally in a giant cell 

 there are to be seen the figures of multiple karyokinesis ; sixteen or twenty V-shaped 

 loops arranged in a ring around the equatorial plate ; or at each end of a nuclear spindle 

 there may be a ring of loops. Sometimes a small, deeply stained nucleus may be seen 

 at a considerable distance from the nuclear heap, and connected with it by a long thin 

 strand of chromatin. 



Occasionally an erythroblast seems to be attached by a pedicle of yellow hyaline 

 protoplasm, continuous with its perinuclear protoplasm to the surface of the giant cell, 

 and more frequently erythroblasts are seen to be lodged in depressions of the surface of 

 the giant cell. The erythroblasts show evidence of active division by karyokinesis ; 

 often five or six cells lying close together all contain figures, and every field of the 

 microscope shows numerous examples. Nucleated red corpuscles, as well as erythroblasts, 

 are readily recognised in films of the fresh pulp fixed by corrosive sublimate. 



In the spleen of the Guinea-pig the pulp tissue is in small amount, being in the form 

 of thin partitions that separate wide venous sinuses. Many of these partitions show a 

 thin-walled axial vessel and correspond probably with the ellipsoidal sheath. The pulp 

 tissue proper seems to be mainly collected around the trabeculse. 



The reticulum is almost identical in appearance with that of the rat. 



The cellular elements are of three chief kinds : — ( 1 ) Lymphoid cells, both uninucleated 

 and multinucleated leucocytes ; (2) coarsely granular protoplasmic corpuscles; and (3) 

 the special vacuolated cells. These si3ecial cells — the so-called blood-corpuscle holding 

 cells — are very numerous, and occur principally in the venous sinuses. They measure 

 from 8 to 16 m in diameter. The smaller consist of coarsely granular protoplasm that stains 

 deeply pink with eosine, surrounding a single deeply blue-stained nucleus, and sometimes 

 a round or oval vacuole. The larger cells have similar protoplasm, occasionally three or 

 four large nuclei without any vacuole, but usually a single nucleus laterally placed, 

 several vacuoles and yellow pigment grains. (Plate III. fig. 14.) The vacuoles sometimes 

 take up nearly the whole of the cell, the remnant of the protoplasm and the nucleus 

 together being in the form of a signet ring around them, the outlines of the vacuoles 

 forming a reticulum that occupies the central cavity. The pigment granules are rarely 

 in a vacuole, — they sometimes seem to be adhering to its inner aspect, — but are 

 usually in the protoplasm that surrounds them. They sometimes accumulate so as to 

 fill the whole cell. 



In the spleen of the Hedgehog the pulp reticulum has a close resemblance to that of 

 the dog and cat ; its cells have many broad plate-like processes, and its meshes are much 

 larger than in the spleen of rodents. It is seen to be continuous with the trabecule and 

 with the walls of the venous sinuses. As in the spleen of the mouse, the presence of 

 giant cells in the pulp is constant, and so is the presence of large coarsely granular pro- 

 toplasmic corpuscles (many of which are vacuolated) in the germinal centres of the 

 follicles. In each of seven spleens, obtained at different seasons of the year, considerable 



