[ no ] 
Additional Observations . 
Received April 27, — Read May 5, 1842. 
92. I have the satisfaction of stating that since the foregoing memoir was pre- 
sented to the Society, many gentlemen have afforded me the opportunity of demon- 
strating to them, either with my own microscope, or with instruments made by 
Powell, Ross, or Smith, the leading facts recorded in it. To one of them (the son 
of an eminent physiologist, Dr. Bostock) I am indebted for sketches of some of the 
appearances he saw. Two of these (figs. 145, 146) represent the filament within blood- 
discs : another (fig. 144) shows a similar filament constituting the muscular fibril. 
At a , this filament is on its edge : at /3, it presents its flat surface. What gives pe- 
culiar value to these sketches, is that they were made by one who then for the first 
time saw the objects in question. 
Facts observed in the Coagulation of the Blood. 
93. In the examination of coagulating blood, discs are seen having two very differ- 
ent appearances : the one kind comparatively pale, the other very red. It is the 
latter discs in which a filament is to be found, and which enter into the formation of 
the clot : the former being merely entangled in it, or remaining in the serum. Ob- 
servers having directed their attention almost exclusively to the undeveloped discs 
so remaining in the serum, it is not surprising that they did not discern the filament 
in question : or that they supposed the blood-discs to be of subordinate importance, 
and to have no concern in the evolution of the fibrin. 
94. In order to see distinctly the filament within blood-discs, some chemical re- 
agent should be added, that will remove a portion of the red colouring matter, with- 
out dissolving the filament itself. I have employed for this purpose either the sub- 
stance before mentioned (corrosive sublimate par. 7), or chromic acid-^, or nitrate 
of silver^, — and chiefly the last. 
95. An objection has been taken to the employment of chemical reagents. It may 
be replied (as suggested by my brother John T. Barry), — if the point to be proved 
by the use of chemical reagents had been, that there exists no visible structure , then 
the use of those reagents would have been objectionable, because of their known de- 
structive tendency in a concentrated state. As, however, the point to be proved is, 
that a peculiar structure does exist, it is not too much to assume, that the appearance 
of a structure so remarkable could not possibly be produced by the chemical action 
of one of those reagents, the mercurial compound for instance, when it is also 
f Sp. gr. about I '040. + A solution consisting of 1 part nitrate silver in 120 water. 
