CHAPTER XII. 



THE INJECTION OF MEDICINES INTO THE BLOOD- 

 STREAM, SUBCUTANEOUS TISSUE, TRACHEA, 

 (ESOPHAGUS. LARYNX, OR PARENCHYMA OF 

 ORGANS OR TISSUES. 



I. 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 micans of a funnel and tube. Apart from the danger of thus 

 introducing air into the vein phlebitis often followed. At the present 

 time syringes with hollow needles are alone used for intravenous 

 injection. They are preferably of considerable size, holding up to i^ 

 fluid ounces, or better still, are double-acting, drawing in the injection 

 fluid on the up stroke and passing it into the vein on the down stroke. 

 This arrangement avoids the necessity for continually removing the 

 needle, and so minimises injury to the intima of the vessel, a fruitful 

 cause of thrombosis and phlebitis. The injection may also be made by 

 means of a funnel and rubber tube connected with the hollow needle. • 



Only certain materials are suitable for intravenous injection ; they 

 must, for instance, at least conform to the following requirements : — 

 They must be fluid, i. e. form perfect solutions without sediment ; for 

 this reason the fluid should be carefully Altered before injection. They 

 must be miscible with the blood. Oils, etc., therefore, may not be used, 

 as they might produce thrombi. They must not undergo any marked 

 decomposition which might lead to clotting of the blood ; so that 

 acids, concentrated alcohol, etc., must be avoided. They must be fairly 

 active, as the injection of large quantities of fluid into the blood-stream 

 might prove disastrous. An exception exists in the case of normal 

 salt solution (-6 per cent, sodium chloride solution) when injected 



