THE FROG 67 
escape from a vessel accidentally cut. It should be made accord- 
ing to the following formula: 
(C@irii:, SINT SB clblbe Ga Gon cetsuiels op dole poooon bioic 400 parts by volume. 
2eperscent- chloral hydrate) 2.1. ace sets ese 400 parts by volume. 
QSMDEGIGEDte alCONOM scr ccvrerescicleieye eieielalsl<leiee) 100 parts by volume. 
Color and glycerin (equal parts) ............ 100 parts by volume. 
Unless the starch is quite free from lumps it should be ground 
in a mortar. 
The colors most commonly used for the arteries are chrome 
yellow (lead chromate), vermilion (mercuric sulphid), and red 
lead. In order to inject the smaller arteries successfully it is 
necessary that the color should be finely powdered and free from 
lumps; it is often advisable to grind it thoroughly in a mortar. 
An extremely fine chrome yellow may be made by dissolving 100 
grams lead acetate and 45.5 grams potassium bichromate each in 
a liter of water. After compete solution, mix and allow the 
precipitate to settle. Pour off the supernatant fluid, and wash the 
precipitate in several waters so as to remove the potassium acetate 
which would injure the specimen. The reaction gives about 100 
grams chrome yellow, which should not be allowed to dry before 
using. 
The constituents of the starch mass should be thoroughly mixed 
by stirring, and the mass strained through muslin, with frequent 
stirring. The starch and color quickly settle, hence the mixture 
must be stirred before using, and occasionally while it is being 
used. It will keep indefinitely. 
For injection select the largest frogs, to be used only for the 
study of the arterial system; they should be killed with ether. 
Open up the body cavity in the same manner as directed in the 
text for the study of the viscera, and cut away all that part of 
the pectoral girdle between the fore-limbs, taking care not to 
leave any sharp projecting points of bone which might injure the 
arteries. Cut away the pericardium so as to expose the heart 
completely. 
For injecting, the writer prefers to use a syringe with glass 
cylinder and metallic frame, of about 10 c.c. capacity ; it should be 
provided with a metallic cannula beveled at the tip so as to present 
a tapering point. It is important that the cannula should be of 
