staining of this substance in an azurophilic di- 

 rection. Because of the mixture of sahnon and 

 bhie colors, the cytoplasm has been given a tex- 

 tural effect that does not occur when the same 

 sti'ucture shows a uniform single hue. Dual 

 coloration of the reticulum gives the optical effect 

 of thickness and density. Of the three structural 

 elements listed, this is the one that offers the 

 best explanation of the "ground-glass effect." 



There is only one other possibility — the pres- 

 ence of definite azurophilic granules. They, 

 however, are relatively rare (figs. 132—135) 

 and thus would not be mentioned as typical for 

 monocytes. Some of the cells shown in the draw- 

 ings came from the same parents that produced 

 the reactive lymphocytes, as has already been 

 stated. The azurophilic bodies may give to the 

 monocyte a tinged margin (fig. 142). The only 

 other cell type that shows a tinged border of this 

 sort is an immature thrombocyte (figs. 296-299 

 and 303). This particular monocyte shows a 

 well-defined Hof that helps to identify it as a 

 monocyte. In other examples drawn from the 

 same family of birds (fig. 132, 134, and p. 65), 

 there is an increasing number of azurophilic 

 granules in tlie cytoplasm. Sometimes they are 

 on the side of the nucleus opposite the Hof; at 

 other times tliey are on the same side; and they 

 may be more or less uniformly scattered over 

 the whole cell. Figure 135 is an extreme ex- 

 ample. Here the azurophilic bodies are larger 

 than normal. They show considerable variabil- 

 ity in staining intensity, and in some respects 

 resemble an early heterophil myelocyte. This 

 type of azurophilic granule is so atypical for 

 monocytes in general that only rarely indeed 

 would a cell of this appearance be picked up in 

 a differential count. 



Hof and orange-staining spheres. — The Hof 

 has been mentioned a number of times as a lightly 

 stained, vacuolated area in the cytosome that has 

 considerable value in the identification of mono- 

 cytes. It may or may not contain orange-stained 

 material. The meaning of the tenn as used here 

 is slightly different from that stated in the broad 

 definition given in Borland's Medical Diction- 

 ary — "The area of the cytoplasm of a cell en- 

 circled by the concavity of tlie nucleus." This 

 definition may fit quite well in some cases. 

 Typical examples of a Hof are shown in figures 

 126, 138, and 144. The clear space in figure 



142 is called a Hof also, although it is obviously 

 not encircled or even bounded by an identation 

 of the nucleus. The area, nevertheless, is clearly 

 demarked from the rest of the cytoplasm. Fig- 

 ures 128 and 133 are good examples of cells that 

 show indented nuclei but there is no Hof in the 

 sense in which the term is used here. The Hof 

 shown in figure 129 is rather indistinct, and in 

 figure 132 it is present as a broad space that fills 

 most of the cytosome on one side of the nucleus. 

 The next three figures contain none. The vacu- 

 olar space opposite the indentation of the nucleus 

 in figure 131 could be called a Hof, as could the 

 clear space in the lymphocyte (fig. 97). The 

 Hof is nearly always found in monocytes but 

 there may be exceptions, as already mentioned. 

 Just how closely associated are the Hof and 

 the rosette obtained with neutral red vital stain 

 is not known. It is assumed that they are closely 

 associated but it has not been determined whether 

 cells that fail to show a Hof, in the sense in which 

 die term is used here, would also fail to show a 

 rosette. 



Specific cell inclusions. — ^The vacuolar spaces 

 of the Hof often contain a homogeneous sub- 

 stance that takes a very faint orange color with 

 Wright's stain, a stain that is better for diis pur- 

 pose than May-Griinwald Giemsa. Perhaps tlie 

 orange spheres could be classed as an azurophilic 

 substance also, although the coloration is dis- 

 tinctly more yellowish than in the small azuro- 

 philic granules described under the heading 

 "Cytoplasmic structure." It takes an excellent 

 light source and microscope correctly used to 

 show any tinge of color in the Hof; yet it is a real 

 substance, as may be demonstrated in the abnor- 

 mal cell, figure 147, where the Hof substance 

 has become concentrated into large spheres. 



All three substances — (1) the azurophilic 

 granules, (2) die azurophilic tinge of the retic- 

 ulum, and (3) the orange spheres of the Hof — 

 are useful in the identification of the monocyte 

 and carry much weight in separating monocytes 

 horn lymphocytes. The only specific cell in- 

 clusions found in lymphocytes are the magenta 

 bodies, which are nearly always darker and more 

 intensely colored than any of the three listed for 

 monocytes. 



Nuclear shape. — Nuclear shape needs very 

 little additional discussion. The difference be- 



69 



