178 NORMAL HISTOLOGY. 



spicuous near their centres, so that the lymphoid cells it contains 

 appear densely crowded ; but toward their peripheries the reticulum 

 is more pronounced and the cells a trifle more separated. At the 

 surface of the Malpighian body its reticulum becomes continuous 

 with that of the pulp surrounding it (Fig. 153). 



FIG. 153. 



Section from human spleen. (Kolliker.) A, capsule ; b, b, trabeculse ; c, c, Malpighian bodies 

 (lymph-follicles), traversed by arterial twigs. In the follicle to the left, part of the 

 arterial twig is seen in longitudinal section ; in that to the right, it appears in cross- 

 section to the right of the centre of the follicle, d, arterial branches ; e, splenic pulp. 

 The section is taken from an injected spleen. 



The relations between the spleen and the blood flowing through 

 it appear to be very similar to those between the lymphatic glands 

 and the lymph passing through them. It seems to act as a species 

 of filter, in which foreign particles or damaged red blood-corpuscles 

 are arrested and destroyed. In many infectious diseases the splenic 

 pulp is increased in amount and highly charged with granules of 

 pigment that appear to be derived from the coloring-matter of the 

 blood. This is notably the case in malaria, in which the red cor- 

 puscles are destroyed by the plasmodium occasioning the disease. 

 When bacteria gain access to the blood they are apt to be especially 

 abundant in the splenic pulp, and it is said that monkeys, which 

 are normally immune against relapsing fever, may acquire the dis- 

 ease if the spleen be removed before inoculation with the spirillum 



