42 FRANK ADAM McJUNKIN 
seen in cover-gloss films of the peripheral blood. To make the 
smears about 5 gm. red bone-marrow crushed with forceps is 
placed in a 15 cc. graduated centrifuge tube with 15 cc. saline 
and shaken vigorously for five minutes, when the suspension is 
filtered through thin muslin moistened with saline and the 
. filtrate centrifuged. The supernatant fluid and as much fat as 
possible is siphoned off. A small drop of the sediment is placed 
on a cover-glass by means of a capillary pipette with rubber 
nipple attached and cover-glass smears made in the usual way. 
The mature polymorphonuclear leucoctyes in smears ‘made in 
this way from dog 151 contain much carbon, but the immature 
ones (metamyelocytes) and myelocytes contain little. The 
comparison of the metamyelocytes with the phagocytic mono- 
nuclear leucocytes present in smears of blood shows that the 
cytoplasm of the former is more acidophilic with a marked 
granulation, while its nucleus is more pyknotic and has the shape 
of a three-quarter segment of a doughnut rather than a slight 
to moderate indentation (kidney nucleus). 
An attempt to prove diminished power of immature _poly- 
morphonuclear leucocytes to ingest carbon by phagocytosis was 
attempted by substituting the suspension of bone-marrow cells 
for blood and performing the test in vitro in the usual way 
(McJunkin, ’18) except 0.2 mg. lampblack is used per cubic 
centimeter of the suspension and the citrate omitted. The 
technic does not give entirely satisfactory results, but serves 
to demonstrate that the phagocytic property of many polymor- 
phonuclear leucoctyes is greater than that of the myelocytes 
and metamyelocytes. 
d. The possible origin of a certain number of the phagocytic 
mononuclear cells of the blood from the endothelial 
lining of the lymph-vessels. 
Two methods of determining whether mononuclear phago- 
cytes enter the blood from the lymp-vessels were utilized. The 
first was to induce in the lymphatics changes that supposedly 
accentuate the activities of the endothelial cells lining the 
