268 DR A. J. WHITING ON THE 



human spleen ; he considers that they are pathological, and that they are composed of 

 " epithelial elements." He found them only in emaciated individuals, and once in a case 

 where death was registered as due to anaemia following haemorrhage. They are, according 

 to our own observation, constant in the child's spleen (the structure of which is always 

 of necessity doubtfully normal), but we have found similar cells in the follicles of a 

 strong adult dog (which was certainly ill nourished and probably also anaemic), in those 

 of a healthy kitten, and in other healthy animals. It seems to us, therefore, that they 

 are not necessarily pathological. Around the follicles there is a zone of fibrous tissue, 

 consisting of tw r o or three layers of nucleated fibres, derived from the hilar sheath. 



In the Human Foetus the cells of the follicles are large, and resemble the cells in the 

 germinal centre of the lower mammals. Very rarely a cell may be seen resembling the 

 protoplasmic corpuscles in the follicles of the child's spleen. The peripheral fibrous zone 

 is more distinct than in the spleen of the child. 



In the Human Adult the majority of the follicular cells consist of a small, round, 

 deeply stained nucleus, surrounded by a rim of granular protoplasm staining pink with 

 eosine. Some of the cells are like free nuclei, and a very small number are large and 

 granular, like the protoplasmic cells in the follicles of the child's spleen. The intra- 

 follicular reticulum is more strongly developed than in any other spleen. 



Summary regarding the Splenic Follicles. 



1. In the fish, amphibians, and reptiles the lymphoid cells form a continuous sheath, 

 of even thickness, around the artery. 



2. In mammals and in some birds the lymphoid cells accumulate in the form of 

 nodular swellings — the splenic follicles — which occur at irregular intervals along the 

 course of the arteries. 



3. The accumulation of lymphoid cells occurs between the hilar sheath and the artery. 



4. Large lymphoid cells (leucoblasts) occupy the middle of many of the follicles in 

 the adult spleen (forming the germinal centre as described by Flemming in lymphatic 

 glands), and by their division give rise to small uninucleated lymphoid cells (as pointed 

 out by Mobius *) which are extruded into the pulp. The small cells are produced both 

 by direct division and by indirect karyokinesis. 



5. The intercellular substance of the follicles consists of two elements, a delicate 

 adenoid reticulum (Muller t, W.) and a viscid albuminous substance (Huxley }). 



G. TJie follicles are surrounded, except where the artery enters and leaves, by a 

 fibro-muscular covering, which is a remnant of the hilar sheath. 



This covering is not a separate membrane, as Sanders § thought, neither is it a 

 condensation of the pulp reticulum as stated by most observers and recently by 

 Bannwarth.|| 



* Mobius (19), p. 343. + W. Muller (12), p. 355. X Huxley (7), p. 81. 



§ Sanders (3), p. 82. || Bannwarth (26), pp. 379, 381. 



