so DISSECTION OF THE VASCULAR SYSTEM. 



canting the excess, and finally mix the chr ornate held 

 in suspension in a little water with tlie plaster-of-Pai'is 

 solution. 



The injection of the vessels is best done as follows : 

 Dissect off the skin and muscles from the ventral sur- 

 face of the thorax. Open the thorax by cutting 

 through the cartilagino2is ribs at their junctiojt with 

 the bony ribs on each side of the stermnii from above 

 the diaphragm to the third rib, then ctU transversely 

 across the sternum aiid remove the piece of thorax 

 thus isolated. On the tinder side of the piece of the 

 stermim left at the anterior end of the thorax rjtn the 

 two sternal arteries and veins ; tJiese nnist be ligated 

 either by dissecting them otitand tying each separately, 

 or by passing a thread rou7id the piece of sternnm 

 and binding firmly. 



Take a large cannula, to which a bit of riMer tub- 

 ing is attached, fill it ivith o.bi solution of NaCl, 

 clamp the tubing, and the^t insert the canmda 

 into the aorta where it springs from the heart and 

 ligature it firmly. Fill the syringe lu it h f he o.6i solution 

 of NaCl and inject it into the aorta, making mcaji- 

 while a ad in the right auricle througJi which the blood 

 call escape. Continue the injection of NaCl solution 

 until all the blood is washed out. Then make the 

 yellow mixture of plaster of Paris and inject it until 

 the arteries are thoroughly filled. If any escape takes 

 place from the small arteries cut in opening the thorax, 

 these arteries can easily be ligated. In this as in all other 

 injectio7is care must be taken not to let air get into 

 the vessel. The rubber tubing on the cannula should be 

 clamped each time the syringe is removed to be filled ; 

 while in filling the syringe one must be careful also 

 to remove all air by holding it in an inverted position 



