320 HANDBOOK OF PHYSIOLOGY. 



Mall has recently described the spleen as consisting of lobules, 

 formed by the trabeculae and contained masses of spleen-pulp. 



The spleen-pull), which is of a dark red or reddish-brown color, is 

 composed chiefly of cells, imbedded in a matrix of fibres formed of the 

 branching of large flattened nucleated endothelioid cells. The spaces of 

 the network only partially occupied by cells form a freely communicat- 

 ing system. Of the cells some are granular corpuscles resembling the 

 lymph-corpuscles, more or less connected with the cells of themeshwork, 

 both in general appearance and in being able to perform amoeboid 



Fig. 228. Reticulum of the spleen of a cat, shown by injection with gelatine. (Cadiat. ) 



movements; others are red blood-corpuscles of normal appearance or 

 variously changed ; while there are also large cells containing either a 

 pigment allied to the coloring matter of the blood, or rounded corpuscles 

 like red corpuscles. 



The splenic artery, after entering the spleen by its concave surface, 

 divides and subdivides, with but little anastomosis between its branches; 

 at the same time its branches are sheathed by the prolongations of the 

 fibrous coat, which they, so to speak, carry into the spleen with them. 

 The arteries then pass into the spleen-pulp, their fibrous coat being re- 

 placed by lymphoid tissue, and end in capillaries, which communi- 

 cate with the lacunar spaces in the spleen-pulp, from which veins arise. 



The walls of the smaller veins are more or less incomplete, and read- 

 ily allow lymphoid corpuscles to be swept into the blood-current. The 

 blood from the arterial capillaries is emptied into a system of interme- 

 diate passages, which are directly bounded by the cells and fibres of the 

 network of the pulp, and from which the smallest venous radicles with 

 their cribriform walls take origin. The veins are large and distensible: 

 uhe whole tissue of the spleen is highly vascular and becomes readily 

 engorged with blood: the amount of distention is, however, limited by 

 the fibrous and muscular tissue of its capsule and trabeculaa, which forms 

 an investment and support for the pulpy mass within. 



On the face of a section of the spleen can be usually seen readily with 

 the naked eye, minute, scattered rounded or oval whitish spots, mostly 

 from sV to sV inch (f to -f mm.) in diameter. These are the Malpi- 



