114 Transactions of the Royal Microscopical Society. 
ever, actual contact. It seemed almost as if one corpuscle were 
attracting or drawing out the thorn-like process from the sur- 
face of the other. In other instances, however, I observed the 
shooting forth and quick withdrawal of these processes from the 
margins of corpuscles not in close vicinity to others (Fig. 61, 
h, c, and d). As these processes appeared at the marginal surfaces 
of the blood-corpuscles, before the latter had come in contact with 
other of their fellows, I naturally regarded the phenomenon as 
one of spontaneous motion, manifested by the coloured blood-cor- 
puscle. But as in most instances the phenomenon was observed 
in corpuscles passing near each other, I was inclined to attribute it 
to a certain power of mutual attraction, residing under certain 
conditions in the coloured blood-corpuscle. Having taken the 
precaution of slightly warming the glass slide before putting the 
blood, quickly taken from the vessels of the skin of a vigorous 
young man, upon it, and the temperature of the surrounding air 
being 96° F., or even more at the time, I also considered a certain 
amount of heat, at least 98° F., as essential to the manifestation of 
the phenomenon. This view, however, proved to be erroneous, as 
I shall show directly. Although I have witnessed this phenomenon 
on blood-corpuscles when in a state of rest, it nevertheless is more 
frequently observed on blood-corpuscles in motion, as when they 
are carried along by a current, arising in the specimen under the 
covering glass, and resembling in character the current of the 
blood in the capillary vessels. With this view the drop of blood 
should be thinly spread upon the glass slide, and quickly covered 
with the thin plate of glass. While the blood-corpuscle is pro- 
jecting the thorn-like process, its body elongates, resembling a 
uni-polar cell, but with the withdrawal of the process, generally 
assumes its original round form; bi-polar or lemon-shaped cor- 
puscles are also frequently met with in specimens of human blood. 
The same process is also observed when the margins of two 
corpuscles actually touch each other very slightly, and then slowly 
separate again. While separating, the thorn-like processes will 
be drawn out at the exact place of contact, and either remain 
permanent, or disappear again after the separation has taken place. 
That the normal heat of the human blood is not essential to 
the manifestation of spontaneous motion in the coloured corpuscles, 
I discovered during the past winter, while repeating my exami- 
nations of the structure of these bodies. I then witnessed the 
phenomenon above described, without having warmed the glass 
slide and covering glass, and at the temperature of a moderately 
warmed room. However, I observed a coloured corpuscle of a 
constricted form, similar to a figure of eight, slowly expanding, and 
finally resuming its original round form (Fig. 61, e and/). 
From this we may conclude that the coloured blood-corpuscle 
