172 OPERATIVE TECHNIQUE. 



to prevent collapse after haemorrhage. LEistly, they must be approxi- 

 mately of the normal body temperature, and as far as possible sterile. 



In consequence, the number of materials fitted for intravenous 

 injection is limited to a few alkaloids, etc., and since the introduction of 

 hypodermic medication even these are less and less frequently given by 

 the veins. The intravenous method has the advantage of producing 

 its immediate effects, while subcutaneous injections require at least 

 four or five minutes, but this advantage is more than offset by the time 

 required to prepare the solutions and the seat of operation previous to 

 intravenous injection. Materials, however, like chloral hydrate, veratrin, 

 etc., which prove locally irritant, and which therefore cannot be 

 given subcutaneously, may be administered by the veins. 



Injection with the ordinary syringe is carried out as follows : — 

 After preparing the solution and carefully bringing it to blood-heat, the 

 operator grasps the shaft of the hollow needle between the index and 

 middle fingers of the right hand, the thumb resting on the broad 

 expanded base. The right jugular vein is compressed with the thumb 

 of the left hand and the needle thrust obliquely downwards through the 

 skin covering the most prominent part of the swollen vein at the spot 

 usually chosen for bleeding. As the animal is often restless at this 

 stage the right hand is simply pressed against the neck without for the 

 moment attempting to introduce the needle further. As soon as it 

 becomes quiet the needle is sharply thrust a little further in the same 

 direction. If the attempt has been successful blood will flow from the 

 open end of the needle when the thumb is removed, showing that it 

 has entered the vessel ; otherwise another trial must be made. The 

 needle is introduced as close as possible to the point compressed by 

 the thumb, as the vein is partially fixed there and is less likely to evade 

 the needle. Once introduced into the vein the needle should be 

 moved as little as possible to prevent injuring the intima. Having 

 satisfied himself that the syringe contains no air, the operator then 

 affixes it to the needle and steadily injects the contained fluid into 

 the vein. 



The double-acting syringe is employed in a similar way. One 

 nozzle is connected by a rubber tube with the needle inserted in the 

 vein, the other by a similar tube with the vessel containing the injection 

 fluid. After injecting the contents of the syringe into the vein the 

 two-way tap is turned and the barrel of the S}'ringe again filled by 

 drawing back the piston. By returning the tap to its original position 

 and once more pressing down the piston a second quantity is injected ; 

 the process can be repeated as often as desired. The method is very 

 convenient, but as it necessitates the application of a sideline or of 



