DESCRIPTION OF PLATES. 163 
blood-serum by them. The latter hypothesis is not 
at all improbable, for these little masses of proto- 
plasm have been seen to pick up granules which 
come in their way in the same manner as the 
amoeba takes its food. For, like the Amcebe, the 
white blood-corpuscles are naked masses of living proto- 
plasm, capable of undergoing active ameeboid movements, 
and also of multiphcation by spontaneous fission. 
To return to the granules in the white corpus- 
cles in yellow-fever blood, it is also possible that 
these are developed im situ,—as the protoplasm 
of the cells in the liver and other organs in this 
disease is changed to a greater or less extent into 
fat (retrograde metamorphosis), and that of the 
white corpuscles may perhaps undergo the same 
change. Be this as it may, the writer has seen 
these corpuscles carrying along their enclosed 
fat-granules, and moving around upon the sur- 
face of a glass slide — under cover, to prevent 
evaporation — forty-eight hours after the blood 
had been removed from the finger of a patient. 
Not because they were in the blood of a fever- 
patient, but because the warm climate of Ha- 
vana is favorable for the long-continued exhibi- 
tion of this remarkable phenomenon, which may 
be witnessed at any time by placing a little drop 
of blood from the finger of a healthy person upon 
a glass slide supported upon a hot stage, by which 
the temperature is maintained at about blood- 
heat. 
The white corpuscles may pass from the blood- 
vessels to the tissues, and when a local inflam- 
