ANODYNES. 503 



the consideration of the therapeutics of the nervous system 

 chiefly from the point of view of symptoms. 



1. Disturbances of Sensation : Pain, and the use of Anodynes. 

 Our review of the physiological and pathological relations of 

 pain leads us to its rational treatment. We must discover, 

 first, its morbid cause, and secondly its exact physiological 

 significance, and apply our measures accordingly. 



The scientific use of anodynes, as we have already suggested, 

 is founded upon correct diagnosis. It will frequently be found 

 that when the cause is known, pain can be removed without the 

 employment of any nervine remedy, and in every instance this 

 treatment should be entertained or attempted. An abscess will 

 be relieved by the knife, headache by purgation, syphilitic 

 periostitis by Iodides. We thus discover a great group of 

 measures which, whilst they are not aneesthetics, are indirect 

 anodynes, because they attack the pathological cause of the 

 pain, and do not immediately act upon nervous tissue. For 

 practical purposes, anodynes may be classified into (1) indirect 

 anodynes ; (2) direct anodynes which act on the peripheral nerves 

 only ; and (3) direct anodynes which act on the centres as well as 

 the periphery. In many instances these may be combined. 



a. Indirect anodynes are necessarily a heterogeneous group, 

 and include surgical operations of every kind, which are amongst 

 the readiest and most radical of all, e.g. opening abscesses, 

 simple physical protectives, such as ointments and oils in 

 burns ; poultices and warm fomentations, and cold in various 

 forms. 



Local irritants, such as mustard and blistering agents, which 

 cause much pain at first, may become local anodynes by pro- 

 ducing an effect which is called counter-irritation. We shall 

 discuss fully this class of remedies in chapter xv., but we 

 may for the present refer their action to exhaustion of the irrit- 

 ability and conductivity of the local nerves, to dilatation of the 

 vessels and relief of anaemia, and to some influence on the nervous 

 centres corresponding to the affected part. Another powerful 

 natural group of local anodynes, which are chiefly indirect, but 

 partly also direct, in their action, consists of the essential oils, 

 such as Turpentine, Camphor, and the Oils of Cloves, Mint, etc. 

 These have a complex action : they destroy the organisms of 

 disease by virtue of being antiseptic ; they dilate the vessels, 

 causing redness and heat; and they depress the peripheral 

 nerves after temporary pain. Certain allied artificial products 

 possess a similar indirect and direct anodyne power, e.g. Car- 

 bolic Acid and Creasote. Besides these local indirect anodynes, 

 we possess an unlimited number which act generally ; as many, 

 indeed, as the remediable causes of pain. Thus, headaches may 



