20 GENERAL ACTIONS OF DRUGS 



Among the drugs more commonly employed for their 

 antiseptic action on the contents of the digestive tract may 

 be mentioned : 



Carbolic acid Bismuth salicylate 



Creosote Bismuth subgallate 



Creolin Sodium sulphite, bisulphite and 



Naphthol hyposulphite . 



Naphthalin Hydrogen dioxide 



Bismuth subnitrate 



Emetics are drugs which cause vomiting. The act of 

 vomiting proceeds from irritation of the vomiting centre in 

 the medulla, which is in close proximity to the respiratory 

 centre. This centre is either acted upon directly by drugs 

 circulating in the blood, or reflexly by agents stimulating 

 sensory nerves in various parts of the body. Thus, irritation 

 of the sensory nerve-endings of the mouth, throat, gullet, 

 lungs, heart, stomach, bowels, biliary passages, peritoneum, 

 uterus and kidneys, may produce vomition. Vomiting is 

 occasioned by simultaneous contraction of the abdominal 

 walls and the diaphragm. In this process the stomach is 

 squeezed between the abdominal walls and diaphragm, and 

 contraction of the longitudinal fibres, radiating from the 

 lower end of the gullet, draws the stomach towards the 

 diaphragm and so pulls open the cardiac orifice, while the 

 pylorus is firmly contracted and closed. Some peculiarities 

 must be noted in reference to vomition in the domestic ani- 

 mals. Dogs, pigs and cats vomit readily and may be placed 

 in the same category as man in this respect. Horses rarely 

 vomit and are not easily nauseated by emetics. Vomiting 

 is prevented in these animals by : 1. The small size of the 

 stonaach, which is not readily compressed between the ab- 

 dominal walls and diaphragm. 2. The length of the gullet 

 between the stomach and diaphragm, which forms a valve- 

 like obstruction when the tube is shortened by contraction 

 of the longitudinal fibres at its lower extremity in attempts 

 at vomition. 3. A- horse-shoe-like band of fibres at the car- 

 diac orifice, which hinders dilatation of this opening. Eumi-* 



