156 Tue Microscors. 
SELECTIONS. 
THE BLOOD-PLAQUE AND COAGULATION. 
The two most notable papers that have appeared for some 
time on the physiology of the blood are “ Cartwright Lectures,” 
by Professor William Osler, on ‘“‘ Certain Problems in the Phy- 
siology of the Blood-corpuscles,” and a paper by Mr. George T. 
Kemp, Fellow of Johns Hopkins University, “‘ On the so-called 
‘New Element’ of the Blood and its Relation to Coagulation,” 
published in Studies from the Biological Laboratory, Vol. III, 
No. 6. Dr. Osler’s first lecture deals exclusively with the blood- 
plaque, while in his third he treats of the relation of the corpus- 
cles to coagulation. 
As is well known, the blood-plaques have been variously 
designated as elementary corpuscles, globulins, granular débris 
or Schultze’s granular masses, hzmato-blasts, and Bluttplatt- 
chen (by Bizzozero). In preference tothe literal translation of 
Bizzozero’s term, blood-plate, both Osler and Kemp have 
adopted the term blood-plaque as being more euphonious. 
Various writers have referred to this element as the “ third cor- 
puscle,” but the objections to this term are so grave that it has 
been practically abandoned. The plaques may be described as 
minute elements circulating in the blood plasma with the other 
corpuscles, and possessing such specific and distinct characteris- 
tics that they must be numbered among the normal histological 
constituents of the blood. Dr. Osler gives their size as from 
one-sixth to one-half that of a red corpuscle. which is sufficiently 
accurate for elements showing such variations in size. Some- 
times, however, a plaque may be found which measures as 
much as 5 mm. It is a circular disc, with a smooth, well-defined 
margin, and occasionally some are found which show a bilateral 
depression. ‘It is a homogeneous, smooth, structureless proto- 
plasm, of a light grey color, and in the unaltered state no nu- 
cleus can be found.” As to whether a nucleus is found after 
staining there is considerable dispute. After the blood has been 
withdrawn from the vessels two peculiarities of the plaques oc- 
casion a serious hindrance to their recognition as special ele- 
ments of the blood: the rapidity with which the protoplasms al- 
ter, and their tendency to adhere to one another and to sub- 
— 
