MICROSCOPICAL PURPOSES. I7l 



tines while the knife is passed through, opening from near the hind 

 legs, well up between the fore-legs. Cut the diaphragm, to allow 

 the fore-legs to spread. Seize the heart with one hand, while its 

 apex is cut off with the knife in the other hand. 



Hold the animal up alternately by head and tail to allow blood 

 to drain out ; wash away the blood. Pass the knife up between 

 the heart and pericardium, slitting up the latter so that it may be 

 pushed up to expose the aorta. Place the animal in a basin of 

 warm water. Do not hurry ; there will be plenty of time for 

 every move. 



If we have cut only a quarter or three-eighths of an inch from 

 the heart, we have opened the left ventricle only, and cannot then 

 pass the syringe canula into the right ventricle in error. 



Hold the heart in the left hand, while with the right the 

 detached syringe canula is run up through the heart, its point 

 passing out into the aorta, using care not to pass it too far up, else 

 it might puncture the arch of the aorta. Now with the right hand 

 pass the curved needle under the aorta, through the tissues between 

 it and the superior vena cava. 



The canula may now be allowed to drop out of the heart 

 while the thread is drawn partly through, and the first half of the 

 surgeon's knot is loosely tied ; then replace the canula and tighten 

 the thread on it, completing the knot. Bring the long ends of the 

 thread up over the hook on the canula, tighten, and again tie it. 



The nose of the stop-cock is now twisted tightly into the 

 canula, while the canula is held in one hand to prevent twisting 

 the aorta. Drop the stop-cock so that it is covered with the warm 

 water while the syringe is being filled. 



When the syringe is slowly filled, close its nose with a finger, 

 rinse the gelatin from the outside of the syringe ; then, placing 

 its point under water, enter it into the stop-cock, holding the latter 

 firmly while the syringe is twisted tightly into it. Hold the nose 

 of the syringe tightly in the one hand, while the piston is managed 

 with the other. This is to prevent damage to the aorta. 



Force the solution very slowly into the animal. We will notice 

 a rapid change in the colour of the animal's nose, pads of the feet, 

 intestines, etc. ; and very often the animal will kick and twitch 

 about for five or six minutes, although it was dead some time 

 before the injecting began. 



