572 APPENDIX. 



Inject an animal which has been killed by bleeding, and before it 

 is cold, and wash out the vessels with warm water, 



2. Heat the injection to a degree of temperature which the finger can 

 bear without pain. If it is colder, the lard solidifies too soon ; if it is 

 warmer, it may shrivel up the sigmoid valves, pass into the left ventricle, 

 thence into the auricle and pulmonary veins, an accident which is also 

 sometimes caused by pushing the piston of the syringe with too much force. 



3. Avoid applying too much force to the piston. 



4. Stop the injection when the arteries react, by their elasticity, upon 

 the piston, so as to drive it backwards. 



Instead of making the injection into the carotid, we may fix a long 

 •curved nozzle into the aortic trunk itself, after having made an opening 

 into the left side of the chest, at the level of the heart, by cutting away 

 two segments of the ribs, and by making an incision into the pericardium 

 over the left ventricle, so as to introduce the nozzle directly into the 

 aorta. This proceeding allows the injection to be as hot as possible, and 

 gives sufficiently good results, because the injection then penetrates, if 

 it be injected under favourable conditions, almost into the capillary 

 vessels ; and ir some organs, forces the injection even into the veins. 



But whichever method is followed, there are certain parts which 

 cannot be ioached by a general injection ; thus a special operation must 

 be performed to force the injection into the vessels of the extremities. 

 After having separated them from the trunk, by sawing them through 

 above the knee or the hock, they are allowed to remain for two hours in 

 a bath of water, kept constantly at a temperature of from 60 to 70 

 degrees, or more, and then they are very easily injected through the 

 posterior radial artery or the anterior tibial, or through any of the other 

 arteries which present their open mouths upon the section of the limb. 

 If we wish to make partial injections of other parts of the body, it may 

 be found easier not to separate them completely from the trunk ; but 

 then the student should take the precaution of cutting ofi" or tying the 

 vessels which establish anastomotic communications between the arteries 

 injected and those which he does not wish to inject. For example, if he 

 wishes to inject the arteries of the head, it is sufficient to inject one of 

 the two common carotids, having tied the other in the middle of the 

 neck, and the two vertebral -arteries in the interstice between the two 

 portions of the scalenus muscle. 



To inject the capillary system, recourse is had to other substances, and 

 to a different method. The following may be used : varnish, alcohol, 

 essence of turpentine, holding in suspension very fine colouring materials, 

 gum arable, dissolved and coloured by any soluble colouring matter, and 

 ijolours ground in oil, or suspended in essence of turpentine. 



