284 DR A. J. WHITING ON THE 



those in the spleens of the younger kittens ; the knobs or lobes seem to be formed and 

 bounded by the mouth-like openings on the surface of the cell. Karyokinetic figures 

 are to be made out in the edant cells. When the cells are treated with nuclear stains 

 alone their protoplasm is seen to have a markedly yellow colour, which, since the tissue 

 was fixed with alcohol only, could not be referred to the use of Muller's fluid or other 

 coloured reagent. 



Young giant cells, a fourth or a fifth the size of the larger ones or less, with 

 coarsely granular protoplasm and undivided nucleus, are somewhat numerous. Most of 

 the giant cells are contained within cell spaces that are apparently formed from the 

 connective tissue strands of the pulp stroma. Grouped in clusters among the giant 

 cells are many erythroblasts, which have an unusually large amount of perinuclear 

 protoplasm, which, like that of the giant cells, stains of a characteristic reddish-violet 

 colour; when no staining agent has been used, it has a yellow tinge. Portions of 

 broken down giant cells occur at frequent intervals throughout the pulp and in numbers 

 within the veins, and in the smaller veins especially are quantities of coarse discrete 

 granules that are apparently derived from the giant cells. 



In the spleen of the ten days old Kitten the giant cells show rather more numerous 

 isolated nuclei than those in the spleens of the other kittens, and many contain erythro- 

 blasts within their substance. Similar cells are more frequently seen within foveolse at 

 the surface of the giant cells than in other spleens, and there is more vacuolation of the 

 giant cells and more erythroblasts grouped round the giant cells than in the two 

 younger spleens ; but while more vacuolation of the giant cells is present than in the 

 seven days old spleen the erythroblasts are not more numerous. Within the veins 

 in the interior of the spleen are numerous giant cells, erythroblasts, smaller nucleated 

 red cells, and, in addition to the ordinary red blood-corpuscles and leucocytes, there 

 are masses of granular protoplasm that are apparently derived from disintegrated 

 giant cells. 



In the spleen of the Kitten six weeks old the giant cells do not show indications 

 of active change as in the two immediately preceding spleens. Their nuclei are usually 

 in a spherical group near the middle of the cell, which is surrounded by a comparatively 

 narrow zone of yellowish granular protoplasm. The nuclear heap occasionally shows 

 slight but large budding, corresponding with which is a large lobing of the cell 

 protoplasm. Protoplasmic corpuscles with the characters of erythroblasts are compara- 

 tively scarce. 



In the spleen of the Porpoise the reticulum is well developed and is more regular 

 than any yet described. The cells composing it are characteristically stellate, and their 

 delicate thread-like processes spring from a comparatively small cell plate. In addition 

 to the rounded meshes there are many long narrow meshes bounded by connective 

 tissue like strands. The whole stroma resembles more connective tissue than endo- 

 thelium. 



The cellular elements of the pulp are mainly of three kinds: — (l) Lymphoid cells; 



