DISEASES OF CATTLE 27 



mechanical. They include gums, mucilage and oils. They lubri- 

 cate and protect abraded or irritable parts from external injury. 

 Given internally they shield the mucous membranes from irritable 

 substances and, to a certain extent, prevent the absorption of poisons. 



Narcotics are drugs which disturb the relation of the mental 

 function with the external world. Examples, alcohol, ether, chloro- 

 form and opium. 



Anodynes relieve pain by diminishing excitability of nerves or 

 nerve centers. They are indicated in cases of colic, pleurisy and 

 pneumonia. Examples, cannabis indica, opium, chloroform and 

 ether. 



Antispasmodics are agents which prevent or remove spasm of 

 voluntary or involuntary muscles. Examples, cannabis indica, bel- 

 ladonna, opium, chloroform and ether. 



Nerve sedatives are agents which lessen nervous excitability. 

 Bromide of potassium' and bromide of ammonium are included in 

 this class of drugs. 



Nerve stimulants are agents which increase nervous excitabil- 

 ity. Example, nux vomica. 



Expectorants facilitate the removal of secretions from the air 

 passages. They are indicated in common colds, pneumonia and, 

 bronchitis. Examples, chloride and carbonate of ammonia, squills 

 and dovers powders. 



Heart stimulants increase the frequency and force of the pulse, 

 and are indicated in debilitating diseases when the pulse is slow and 

 feeble. Alcohol and the ammonium preparations are examples. 



Heart sedatives decrease the frequency and force of the pulse, 

 and are used in febrile diseases when the pulse is rapid and strong. 

 They should not be used when the pulse is weak. Aconite is an 

 example. 



Purgatives are agents which cause intestinal evacuations. When 

 their action is mild they are termed laxatives. 



Vermicides are agents which destroy parasites, such as round 

 worms and tape worms in the digestive tract. Santonin and areca 

 nut are included in this class of drugs. 



Diuretics are agents which act on the kidneys and increase the 

 flow of urine. They are divided into two classes, stimulating and 

 refrigerating. Stimulating diuretics increase the flow of urine by 

 increasing the blood pressure in the kidneys, and should never be 

 used in inflammatory diseases of the kidneys. Refrigerating diur- 

 etics act by increasing the cell protoplasm of the kidneys, and have 

 a cooling effect on those organs. They are indicated in febrile dis- 

 eases when the kidneys are inactive, and in inflammation of the 

 kidneys. The potassium and lithium salts act as refrigerating diur- 

 etics, while sweet spirits of nitre, alcohol and other stimulants act 

 as stimulating diuretics. 



Tonics are agents which impart tone or strength to the parts 

 on which they specially act. It is a notable fact that all drugs which 

 have a tonic action do not produce their effects in the same manner. 

 Gentian acts as a stomach tonic, aids digestion and, hence, tones up 



