SUBCUTANEOUS INJECTIONS. 



64^ 



producing local effects, as, for instance, with cocaine (p. 619), in 

 which case the injection is made deeper than usual, or it is made 

 close to the nerve on which it is required to act. Medicines given 

 hypodermically do not come in contact with the food in the 

 stomach and intestines ; and thej' escape the changes which many 

 substances undergo in the liver, and hence act more certainly. 

 Economy in drugs is a further item for consideration. The chief 

 disadvantage of this method is that it is not suitable for certain 

 medicines, such as oily substances, which are very slowdy absorbed 

 by the subcutaneous tissue ; bulky agents, like Ep.som salts ; and 



Fig. i6o. — Read's enema pump. 



irritating drugs, like turpentine. The bad effect due to the 

 introduction of putrefactive, material into the wound can be 

 entirely obviated by strict antiseptic measures (p. 70). 



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. The solutions should 

 be neuter in their reactions, or only slightly acid ; free from solid 

 particles and all impurities ; and as concentrated as the nature 

 of the medicine will admit, so that absorption may not be retarded. 



