4.90 ARMAND RUFFER. 
If the tissue immediately below the epithelial border be 
now examined other characteristic cells attract the observer’s 
attention. In sections carefully and deeply stained with alum- 
carmine or hematoxylin large mononucleated cells are seen 
lying scattered between the lymphocytes. 
The drawings (figs. 1 to 15) give an exact representation of 
these cells, after the section has been stained with alum- 
carmine and gentian-violet. The size of one of these structures 
when fully developed is enormous if it be compared to that of 
the lymphocytes surrounding them; and, taking into account 
their size and their functions, they must be included under the 
class of cells to which M. Metschnikoff has given the name of 
macrophages. 
The nucleus of a macrophage is always single, varies in size 
according to that of the cell, becoming larger as the latter 
increases, and may be twice or three times the size of that of an 
ordinary lymphocyte (see figs. 1—7, also fig. 10). It is 
sometimes round, more frequently oval, or even of a horseshoe 
shape. The different forms may possibly be due to their being 
cut across obliquely by the knife. The nucleus has often two 
or three nucleoli together with a very fine and delicate reticulum 
staining well with carmine or hematoxylin. The protoplasm 
of the macrophage is quite homogeneous, of a pale rose colour 
after the action of alum-carmine, or of a pale violet hue after 
being stained with hematoxylin. The protoplasm often con- 
tains large vacuoles (see figs. 15, 18, 19). The contours of 
the whole cell are sometimes quite round ; sometimes, however, 
irregular (see figs. 7, 8 dis, 12). The occasional irregularity 
of shape is an argument in favour of the supposition that 
these cells are contractile, and therefore probably mobile, 
having been fixed by the alcohol at a time when, being on the 
march, they had altered their shapes. Other facts to be 
enumerated later on confirm the supposition that these cells 
are mobile structures. 
The contents of these macrophages are interesting to study, 
for in their interior are found dead and living leucocytes, nuclei 
of partially digested leucocytes, together with fragments of 
