292 The Philippine Journal of Science 1916 
larged and vacuolated and frequently desquamated. Large. cells, 
which are apparently derived from these, are found lying free 
in the sinuses. Their nuclei are single or they may he double. 
Cells no larger than these are also seen with as many as 10 or 
12 closely packed nuclei and with very indefinite cytoplasmic 
structure. The origin of these latter cells was not determined; 
they may be derived from the endothelium lining the sinuses, 
or they may be marrow cells. It is not unusual to find consid- 
erable numbers of polymorphonuclear leucocytes lying among the 
cells of the splenic pulp. 
The condition of the lymphoid follicles varies. In a fair 
percentage of the cases they are normal in size, and in no case 
of this series were they noticeably enlarged. Diminution in 
size and relative scarcity of the follicles is frequently seen. 
The central vessel in the follicles is usually engorged, and its 
walls appear thickened and poor in nuclei with a fibrillated 
structure which is eosinophilic. The adventitia is loose, and 
there is frequently a clear space immediately about the vessel. 
The entire structure of the follicles is loose and open, the lym- 
phocytes being separated from one another. Evidence of hy- 
perplasia of the follicles, as manifested by enlargement and 
mitotic figures of the cells in the germinal centers, is not fre- 
quently seen in plague. Bacilli within the follicles are never 
numerous. Hzmorrhages from the surrounding pulp may ex- 
tend into and break up the follicles. In some cases the con- 
gestion of the spleen is most marked about the follicles, as has 
been noted previously in pneumonic plague, but this feature is 
not so noticeable and not nearly so constant in the spleens of 
this series. 
The trabecule show the same evidences of hyaline degenera- 
tion and frequently necrosis, as has been described in the walls 
of the blood vessels and the trabecule in the buboes. Small 
localized areas of hemorrhagic necrosis occur throughout the 
spleen in a large proportion of the cases. In these one sees 
large numbers of erythrocytes with very few other formed 
cellular elements, but large masses of chromatin particles. 
Larger infarcted areas were visible to the naked eye in three 
of our cases, as noted previously. These infarcted areas are 
rich in bacilli. Plague bacilli are almost always present in the 
spleen in rather large numbers, but they do not occur in the 
large zodgleal masses such as are seen in the buboes. They 
are more widely scattered through the splenic pulp, in the sin- 
uses, and in the endothelial cells. They are sometimes seen 
