634 ADMINISTRATION OF MEDICINES 



MEDICINES FOR HYPODERMIC INJECTION AND THEIR 



DOSES. — " The drugs most suitable for subcutaneous injection 

 are liquids which can be mixed with water, and soluble solids, par- 

 ticularly alkaloids. Distilled water is the best vehicle, and after 

 it, alcohol and glycerine, properly diluted" (L. Guinard). The 

 solutions should be neuter in their reactions, or only slightly acid ; 

 free from solid particles and all imjDurities; and as concentrated 

 as the nature of the medicine will admit, so that absorption may 

 not be retarded. Druggists issue medicines for hypodermic in- 

 jection in exact doses in hermetically closed tubes, and in tabloids 

 of particular weights. 



Guinard (" Encyclopedie Veterinaire ") gives the following 

 strength for hypodermic injections : — 



Aloin, 10 to 20 p.c. 



Cocaine, 2 to 5 p.c. 



Eserine, | p.c. 



Salts of morphine and pilocarpine, 2 p.c. 



Strychnine, ^^ p.c. 



THE OPERATION AND ITS SEAT.— These injections are made 

 by a syringe (Fig. 156) which has a glass barrel and a hollow 

 needle. The most suitable substance for the manufacture of the 

 needle is an alloy of platinum and iridium, which is hard, rigid, 

 and practically indestructible. It is well to have the piston of 

 asbestos, so that the syringe can be rendered free from putrefactive 

 germs by immersing it for a few minutes in boiling water, which 

 in this case will not injure it. In order to prevent the introduction 

 of putrefactive or infective material under the skin by this opera- 

 tion, we should, if possible, do it under antiseptic precautions (p. 

 70), that is to say, we should disinfect the part, our hands^ and 

 the syringe, and should take care that the solution for injection is 

 free from contamination. For producing a general effect, it is ad- 

 visable to choose a spot where the skin is thin and loose, so that the 

 puncture may be easily made, and the injected fluid may have plenty 

 of room to become widely distributed. On this account, these 

 injections are generally made behind or in front of the lower part 

 of the shoulder, or on the breast. After the syringe has been filled, 

 it should be held with its point uppermost and the piston slightly 

 pressed, to permit the escape of the bubble of air which might other- 

 wise remain ; because the entrance of air under the skin might give 

 rise to an abscess. A more or less horizontal fold of skin, at the 

 spot chosen, is taken up between the finger and thumb of the left 

 hand, and the point of the syringe, which is held in the right hand, 

 is passed perpendicularly through the base of the fold, and is 

 carried a little onwards, between the skin and the flesh, which we 



