72 ANTISPASMODICS 



veratrine, carbolic acid and other phenols ; by menthol and 

 thymol, local blood-letting, heat and moisture as by poul- 

 tices and fomentations, and by cold, in the form of ice or 

 cold water. Counter-irritants also act reflexly as analgesics. 



When pain is not localised, general anodynes are adminis- 

 tered, either by the mouth or hypodermically. Many act 

 mainly as sedatives or paralysants of the brain centres. 

 Chloral hydrate, Indian hemp, hemlock, bromides, and 

 anaesthetics are types of this class. Others with little or no 

 central action paralyse sensory nerves or nerve-endings, 

 and so prevent painful impulses being received. These are 

 exemplified by atropine, cocaine, and aconite. Opium and 

 morphine produce their anodyne effects by depressing 

 sensory nerve-cells of the brain and cord, although they have 

 little or no effect on sensory nerve-endings and so are of 

 little use applied locally. Several of the newly-discovered 

 bodies of the benzol or aromatic series conjoin antiseptic and 

 anodyne properties. Such are salol, a salicylate of phenol ; 

 antifebrin, which controls many varieties of pain ; while 

 exalgin is still more generally effectual. Salicylic acid and 

 salicylates have a special power of controlling the pain of 

 acute rheumatism. Electricity applied along the course of 

 the stimulated nerves, and, in acute rheumatism, nerve- 

 stretching, are sometimes tried. Dividing the nerves 

 supplying the seat of injury, as is done in navicular and some 

 other diseases of the feet, prevents the feeling of pain, but of 

 course does not arrest local inflammation or other mischief. 

 In horses, as in other animals, the giving of a dose of physic 

 and the administration of tonics are often effectual, prob- 

 ably owing to their relieving irritability of the cerebro- 

 spinal centres, by removing waste material, and by a general 

 improvement in tone. 



ANTISPASMODICS are agents which prevent or lessen 

 muscular spasm, which is an irregular painful contraction 

 of voluntary or involuntary muscles. In the medulla 

 oblongata, where it joins the pons, and related to the respira- 

 tory centre, is a centre which, when stimulated, causes 

 general convulsions and spasms. These are excited by 

 direct irritation of the centre with chemical agents, by 

 contact action of such poisons as strychnine, nicotine, picro- 



