The Structure of Colored Blood- Corpuscles. 301 



in those of man in a number of instances. He reports that he 

 had witnessed the phenomenon in the colored blood-corpuscles of 

 man as early as the summer of 1871. He says, "In examin- 

 ing a specimen of human blood, and whilst my attention was 

 directed to the colored corpuscles as they were carried along by 

 a moderate current of the liquor sanguinis under the covering 

 glass, I noticed on some of them the projection and immediate 

 withdrawal of minute, conical, thorn-like processes, whenever 

 one blood-corpuscle came into the vicinity of another, without, 

 however, actual contact. It seemed almost as if one corpuscle 

 were attracting or drawing out the thorn-like process from the 

 surface 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. 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 colored blood-corpuscle. 

 But as in most instances the phenomenon was observed in cor- 

 puscles passing near each other, I was inclined to attribute it to 

 a certain power of mutual attraction, residing under certain 

 conditions in the colored blood-corpuscles. 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 mani- 

 festation of the phenomenon. This view, however, proved to 

 be erroneous, as I shall show directly. Although I have wit- 

 nessed this phenomenon on blood-corpuscles when in a state of 

 rest, it nevertheless is more frequently observed on blood-corpus- 

 cles 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 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 projecting the thorn-like process, its body 

 elongates, resembling a unipolar cell ; but with the withdrawal 

 of the process, generally assumes its original round form ; bi- 



