636 ADMINISTKATION OP^ MEDICINES. 



By Puncture into the large Intestine. 



The bowel is first punctured by a trocar and cannula, and 

 when the trocar is withdrawn, the medicine is injected into the 

 cannula, which conveys it into the intestine. We must observe 

 the precaution "that the cannula is still in the bowel when the 

 solution is injected. This is shown by a small amount of gas being 

 expelled with each respiratory movement " [Bradley). If the 

 solution, instead of flowing into the bowel, falls into the ab- 

 dominal cavity, death may ensue from peritonitis (p. 114). The 

 danger of this accident naturally decreases the popularity of this 

 operation. 



By a Yein, 



This (intra-venous) method of injection is very rarely practised 

 by veterinary surgeons, but it will certainly be widely 

 adopted in the near future, on account of its great value in 

 directly attacking infective agents in the blood, such as those of 

 septicaemia (p. 532). Strict antiseptic precautions (p. 70) should 

 be observed, and great care should be taken to avoid the formation 

 of blood clots and the introduction of air into the vein. Blood 

 clots might form a thrombus (p. 118), and air carried into the heart 

 might easily kill the animal. A small incision into the skin at the 

 seat of operation may be necessary to facilitate the introduction 

 of the needle, and we should be particularly careful to keep the 

 point of the needle in the centre of the blood-vessel, and not to 

 pierce its other side. We should, of course, bear in mind that the 

 blood stream in a vein proceeds towards the heart. The jugular 

 vein (p. 118) is the most convenient one to operate on. The in- 

 jection should be made very slowly, and its effects should be care- 

 fully noted. It is well to remember that some medicines, as, for 

 instance, Epsom salts and Glauber's salts, do not have the same 

 action when injected into a vein as they have when taken by the 

 mouth. 



By the Skin. 



When the skin is in a normal condition, its power of absorption 

 as a rule is almost nil ; but when it is inflamed, it can readily take 

 up the active principles of many medicines, as we may see by the 

 irritating effect which extensive cantharides blisters, applied to the 

 legs, have on the kidneys. The antiseptic action of biniodide of 

 mercury on the microbes of pus in more or less deep-seated tissues. 



