276 DR A. J. WHITING ON THE 



consist, like the reticulum of a lymph gland, of a network of fibres with cells super- 

 imposed at the nodes. 



The corpuscular elements of the pulp are mainly of four kinds : — (l) Round or oval 

 lymphoid cells, measuring 3-7 v-. in diameter, which stain deeply with hsematoxylin, 

 and resemble the cells forming the outer zone of the follicles. They have only a very 

 small amount of peripheral protoplasm, if any. (2) Protoplasmic corpuscles of oval shape, 

 consisting of a round or oval nucleus surrounded by a considerable amount of pink- 

 stained protoplasm,* and measuring 7-10 m. in diameter. (3) Cells containing pig- 

 ment resembling in size and shape the protoplasmic corpuscles. (4) Giant cells, consisting 

 of coarsely granular protoplasm which stains deeply pink with eosine, and in which are 

 imbedded several nuclei. The usual shape of these cells is lobed oval, and their average 

 measurement is about 30 m long by 15 m broad. 



In the Skate the reticulum of the splenic pulp is composed of a branching system of 

 expanded fibres which stain faintly with eosine, and which are connected with narrower, 

 stronger, more deeply stained fibres. The expanded fibres are sections of the plate-like 

 processes of branching nucleated cells. The narrower stronger fibres seem to be the 

 walls of the venous radicles ; they are frequently crescentic in shape, and have on their 

 inner concave surface a layer of endothelial cells. 



The cells of the pulp are of four principal kinds : — (1) The most numerous are clear, 

 round cells like free nuclei. They stain faintly with hsematoxylin, the chromatin 

 particles being arranged in a ring near the periphery of the cell. Their average size 

 is about 8 /x,. (2) Less numerous cells consisting of granular protoplasm that stains 

 pink with eosine, surrounding a round, oval or horse-shoe shaped nucleus. These cells 

 resemble some of the cells contained in the representatives of the follicles. (3) Cells like 

 the protoplasmic corpuscles, but containing pigment granules of different sizes. These 

 resemble the majority of the cells of the follicles. (4) Cells similar in size and shape to 

 the third variety, but vacuolated, the vacuoles containing rounded particles of pigmented 

 protoplasm which have no nuclei and are about a fourth of the size of the coloured blood- 

 corpuscles. 



In the Cod and Ling the reticulum of the splenic pulp consists of anastomosing plate- 

 like processes of nucleated cells as in the skate, but the meshes are apparently wider. 

 The cells of the cod's spleen are mainly of three kinds: — (l) Round lymphoid cells of 

 different sizes, sometimes possessing a narrow rim of protoplasm, but usually like free- 

 nuclei. (2) Protoplasmic corpuscles varying in size from about a half to a little more 

 than the size of their average red blood-corpuscle. Both protoplasm and nucleus stain 

 with hsematoxylin, the former faintly, the latter somewhat deeply. The larger have the 

 size and shape of the coloured blood-corpuscles. (3) Cells containing pigment occur 

 here and there in clumps. 



* Whenever the phrases "pink-stained protoplasm" and "blue-stained nuclei" occur in the text they mean 

 respectively "protoplasm that has been stained pink with eosine" and "nuclei that have been stained blue with 

 hematoxylin." 



