718 Plaster of Paris as an Injecting Mass. [ November, 
be heated before use. The subject must also be thoroughly 
warmed, | 
Plaster of Paris has long been used as an injecting mass, in the 
medical schools of this country at least. It seems to be admirably 
adapted to this purpose from its well known property of becoming 
solid when mixed with water. 
Although plaster has not the defects of the masses that require 
warming before use, there are difficulties in its manipulation. I 
have been unable to find anything upon the matter in books; and 
gentlemen connected with medical schools say they do not 
know of any printed directions; but this process of injecting, 
like other expedients is handed down by tradition from one dem- 
onstrator to another. All that I have been able to learn from 
others of the technology of plaster injections is that the plaster 
should be mixed to a thin paste with water (with a saturated 
aqueous solution of arseniate of soda at one medical school) and 
used, uncolored or colored with vermilion or red lead, very 
quickly before it has time to set. 
The lack of precise information as to its manipulation, and the 
skill and certainty necessary to use simple plaster and water, 
from its rapid setting, render it hardly manageable by students. 
Yet it is so simple and excellent for coarse injections that some 
careful experiments were made, in the anatomical laboratory of 
the Cornell University during the last college year, to render it 
practicable, if possible, for the use of students by elucidating the 
following particulars: 
The character of the plaster to be used. 
The proportions of plaster and fluid. 
The best and cheapest red and blue colors. i 
The means by which the plaster may be kept fluid ten to thirty minutes after mix- 
ing without preventing it from hardening finally. 
The precautions necessary in making permanent the preparations injected with 
h 
bash ate ieee 
iy 
(1.) It was found that the very finest plaster is best, and indeed 
_ necessary if it is desired to fill the smaller vessels. 
(2.) Equal volumes of plaster and fluid give the best results. 
This forms a very fluid mass which penetrates finely and sets firmly. 
1 According to Martin and Frey (7, II, ror and 10,174), fine cold flowing inject- 
_ ing masses may be made by dissolving copal and mastic resin, with a small propor : 
tion of wax, in sulphuric ether, and coloring with red lead; or by dissolving the 3 
finest red sealing-wax w Cees os These masses harden as soon as ie 
sr Or siropo soaks into the 
