174 INTRAVENOUS, SUBCUTANEOUS, AND OTHER INJECTIONS. 



XIV.— THE INJECTION OF MEDICINES INTO THE BLOOD-STREAM, 

 SUBCUTANEOUS TISSUE, TRACHEA, PHARYNX, LARYNX, OR 

 PARENCHYMA OF ORGANS OR TISSUES. 



(a) Intravenous injection. In former times bleeding was often 

 a preliminary to intravenous injection of medicines. In horses, for 

 instance, the jugular vein was opened with the fleam, and the 

 medicine injected by means of a funnel and tube. Apart from the 

 danger of thus introducing air into the vein phlebitis often followed. 

 At the present time a fine trocar and cannula, or a syringe with a 

 hollow needle is used for intravenous injection. In horses and cattle 

 the jugular vein, and in dogs the saphena vein are the vessels selected 

 for the introduction of remedies into the circulation. The number 

 of materials fitted for intravenous infection is limited to a few 

 alkaloids, antitoxins, normal saline solution ("9 per cent.), barium 

 chloride, silver colloid, chloral hydrate, etc. The intravenous method 

 has the advantage of producing 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 solution and 

 the seat of operation previous to intravenous injection. The fluid 

 for injection must be diluted, non-irritant, and aseptic. 



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

 After disinfecting the skin at the seat of injection, 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. 



