28 



EXERCISE V 



vagus, and 

 influence of 

 adrenal extract 

 upon. 



stimulation until the ventricle escapes (text-fig. 13 c), i. e. begins to beat ; after 

 the slow ventricular beat has established itself for 3-4 sees., cease faradization. 

 Inject -5 c.c. of weak adrenal extract with the needle-syringe per venam, andj 

 after the arterial pressure has fallen to its previous level, repeat faradization ; 

 the ventricle will be found to escape earlier than it did before. To inject with 

 the needle syringe per venam use the following procedure : 



VII. Intravenous injection of drugs (text-figs. 14, 15). In the decapitate 

 preparation the veins are usually rather fully distended, the arterial tonus 

 being low. This makes injection into them the more easy. If the quantity 

 of fluid to be injected is, as with atropine, ' adrenalin', 'pituitrin', &c., not 

 more than 4 c.c, it can be introduced conveniently by a needle-syringe. 



To do this, the syringe, without its needle, is filled with saline and the 

 efficiency of the piston tested. The needle is preferably not a straight one, but 

 bent to a slight angle about half-way down its length. This bend can be 

 easily made when the needle is heated in a small flame. With the syringe 

 filled, the fit of the needle to the nozzle is tested and the needle tried to see 

 that it is not blocked. The syringe is next filled with the needle off, and all 

 air expelled carefully by holding the syringe vertical with nozzle upward 

 and driving it out by the piston, then taking up further from the vessel 

 containing the solution enough to completely fill the syringe. The needle is 

 then pushed firmly upon the nozzle and air expelled from the needle, holding the 

 syringe vertical as before. The metal guard on the piston-handle is then 

 screwed to the appropriate place for delivery of the dose decided on. The 

 syringes, if not marked in c.c, are usually marked off in one-twentieth divisions 

 of their capacity ; 15 of these make very approximately 1 c.c The loaded 

 syringe is then placed ready to the right hand. 



A vein suited for injection is the internal saphenous ; a good point in it 

 lies 2-3 cm. above the ankle. To use the vein there (text-fig. 14) the limb is 

 kept straightened by the string- weight clip attached to a digit. As a guide 

 a line (text-fig. 14) is taken on the front of the ankle from midway between 

 the malleoli to the mid-point of the median aspect of the knee. The 

 operator stands to the preparation's right-hand side. In this line where it 

 crosses front edge of subcutaneous face of tibia, about 2-5 cm. above the 

 malleoli, a fold of skin in the direction of the line is picked up between thumb 

 and forefinger of left hand, and, with large scissors in the right hand, this fold 

 is cut from below upward ; the cut is not carried farther than to leave the flap 

 still attached above. On releasing the fold a button-hole wound exposing the 

 vein results. Any layers of connective tissue covering the vein are picked up 

 carefully with fine forceps, and cut off with fine scissors till the vein lies 



