PHAGOCYTIC ACTIVITY OF THE SPLEEN 439 



NORMAL SPLEEN 



In the spleen of the normal rabbit can always be found phago- 

 cytic cells with inclusions. The detection of these cells is greatly 

 facilitated by spreading apart the constituent tissues of the spleen 

 pulp by intravascular injection of fluids. Although part of the 

 blood content is driven out by this procedure, one can never force 

 out all the blood, and the great advantage is that the resultant 

 preparation is much more easily studied. 



The largest of these phagocytic cell types are the free-swimming 

 mononuclear cells, called splenocytes. These vary in size accord- 

 ing to the bulk of their contents. The nucleus tends to be 

 rounded or oval in shape, and is usually eccentrically placed. 

 The nuclear membrane is very well defined, and the chromatin 

 is distributed in one or two larger dots and in a network of fine 

 lines. In general the nuclear contents are pale-staining, as com- 

 pared with the nuclear membrane. The most evident character- 

 istic in the cytoplasm is the presence of inclusions. These inclu- 

 sions are sometimes single, but are usually multiple. They are 

 most frequently in the form of light yellow spots embedded in 

 the cytoplasm. Indeed, a useful method of detecting the spleno- 

 cytes is to search over the microscopic field for little clusters of 

 golden-yellow dots. If such a cluster is in a closely compacted 

 mass of cells, diagnosis of the containing cell is very difficult. 

 But if the cell lies free within a pulpar blood space, then the 

 configuration of the cell is readily seen, as shown in figure 1. 

 These contained spots are of varying size, and may not all be 

 of exactly the same color. Sometimes they are closely packed, 

 making a nearly homogeneous mass. In other cells the dots are 

 farther apart, so that the intervening cytoplasm is seen between 

 them. All these appearances are regarded as products of the 

 intracellular digestion of entire erythrocytes, or fragments of 

 them, in the form of hemosiderin. In testing for iron in such 

 cells, these clusters of dots give a strongly positive reaction. 

 Occasionally one sees what appears to be an entire red blood 

 corpuscle still intact within the splenocyte, but final judgment 

 is often difficult. Or again, the inclusions may appear as hemo- 



