PRACTICAL EXERCISES 187 



lower ligature firmly around its neck. The upper ligature can now 

 be withdrawn. 



Clip off the hair on each side of the sternum. Make an incision 

 on each side through the skin and down to the costal cartilages about 

 2 inches from the edge of the breast-bone, and long enough to 

 expose about four costal cartilages (say, 3rd to 6th) . With a curved 

 needle pass waxed ligatures round the cartilages, and tie firmly to 

 compress the intercostal vessels. The bellows should now, or earlier 

 if any symptoms of impeded respiration have appeared, be connected 

 with one end of the horizontal limb of a glass T-piece, the other end 

 of which is similarly connected with the tracheal cannula. The 

 stem of the T-piece is provided with a short piece of rubber tubing, 

 which, when artificial respiration is being carried on, is to be alter- 

 nately closed and opened closed during inflation of the lungs, and 

 opened when the air is to be allowed to escape from them. Or a 

 screw-clamp may be adjusted on the piece of tubing so that the 

 opening is sufficiently narrow to permit the lungs to be properly 

 inflated when the bellows are compressed, and yet sufficiently wide 

 to permit easy escape of the air and collapse of the lungs at the end 

 of each inflation. Ether may, when necessary, be administered, by 

 inserting between the T-piece and the tube from the bellows an ether 

 bottle with two tubes passing through the cork to within an inch 

 or two of the ether. If the cannula has a side-opening, as is usually 

 the case with metal cannulae, the T-piece may be dispensed with. 

 One student should take sole charge of the artificial respiration, 

 which ought to be begun as soon as the chest has been opened, and 

 continued at the rate of about twenty inflations per minute. The 

 costal cartilages are rapidly cut through with strong scissors just on 

 the sternal side of the ligatures, the artificial respiration being 

 -suspended for an instant, as each cut is made, to avoid wounding 

 the lungs. The sternum is divided at its lower end and turned up. 

 If there is much bleeding a ligature should be tied round its upper 

 end. With a curved needle a ligature is passed below the internal 

 mammary arteries as they approach the sternum. That bone may 

 now be removed, and the heart, enclosed in the pericardium, comes 

 into view. A thread is passed with a suture-needle through each side of 

 the pericardium, which is then stitched to the chest-wall and opened. 



(a) Note the various portions of the heart, right and left ventricles, 

 right and left auricles, with the auricular appendices. Feel the 

 heart with the hand, and observe that the right ventricle is softer 

 and has thinner walls than the left, and that the auricles are softer 

 than the ventricles. Note how all the parts of the heart harden in 

 the hand during systole and soften during diastole (pp. 78, 82). 



(b) Dissect out the vago-sympathetic on one side in the neck 

 of the dog. The guide to the nerve is the carotid artery. These 

 two structures and the internal jugular vein lie side by side 

 in a common sheath. Feel for the artery a little external to the 

 trachea, cut down on it, open the sheath, isolate the vago-sympathetic 

 for about an inch, pass two ligatures under it, tie them, and divide 

 between the ligatures. The peripheral and central ends of the 

 nerve may now be successively stimulated. Stimulation of the 

 peripheral end causes slowing of the heart, or stoppage in diastole. 

 Feel that it softens when it stops. It soon begins to beat again. 

 Stimulation of the central end of the vago-sympathetic may or may 

 not cause inhibition. If it does, expose the other vago-sympathetic, 

 divide it, and repeat the stimulation of the central end. There will 



