APPENDIX. 571 



The Heart. — Place the animal in the second position ; remove the 

 sternal ribs, separating them from their cartilages ; then dislocate the 

 costo-vertehral articulations. Tliis dissection permits the study of the 

 situation and general disposition of the heart and of the pericardium. 

 To examine with ease the reciprocal arrangement of these two organs, 

 remove them from the thoracic cavity by detaching the sternal insertion 

 of the pericardium. 



Preparation of Arteries. — The preparation of arteries consists of 

 two successive operations — 1. Injection; 2. Dissection. 



Injection of Arteries. — Injection is an operation consisting of the 

 introduction into the interior of the vessels of a solidifiable substance, 

 intended to give to their canals the volume and conformation which they 

 present during life, when they are filled with blood. Lard mixed with 

 lamp-black is the material usually employed. Another injection some- 

 times used consists of gelatine, mixed with a certain quantity of plaster 

 of Paris ; but this is little used in the French school. A copper or 

 brass syringe and a nozzle, fitted with a stop-cork upon the extremity 

 of the syringe, is necessary for pouring the injection into the arterial 



The method of making a general injection is as follows : — The animal 

 having been laid upon a table, the carotid artery is laid bare by means 

 of an incision made in the jugular gutter. The vessel is opened longi- 

 tudinally. A ligature is applied above the opening, and the nozzle is 

 securely fixed in the artery, upon the cardiac side, by aid of a second 

 ligature. The injection, prepared beforehand, is drawn into the syringe. 

 The syringe is then carefully screwed upon the nozzle, and the piston is 

 pushed steadily onwards, so as to make the injection pass into the 

 arterial canals. 



The following form useful injections : — 



Lard, or Tallow, . . .9 parts. 



Oil of Turpentine, . . . 1 j, 



Colouring Matter, . . . 2 „ 



Bees'- wax, ... .1 part. 



Tallow,. . . . . 8 „ 



Colouring Matter, . . , ad lib. 



Lamp-black, Indigo, and Prussian blue may be used for the veins; 

 for the arteries, as vermillion is expensive, Venetian red mixed with red 

 lead is a good substitute. 



To succeed well in this operation, attend carefully to the following 

 precautions : — 



