ANMSTHETICS. 499 



which, in appearance at least, closely resembles sleep, and is 

 associated with suspension of all the other mental faculties. 

 This effect may be secured by temporarily arresting the func- 

 tions of the convolutions by means of drugs which directly de- 

 press the nervous tissue of the convolutions, such as Chloroform, 

 Ether, Bichloride of Methylene, Alcohol in large doses, Chloral, 

 and Opium. The Bromides, Caffein and Zinc, are valuable 

 cerebral depressants, as they diminish reflex excitability, and 

 thus promote rest of the nervous centres. Beyond these, a 

 number of powerful substances, such as Aconite, and other 

 vegetable and mineral poisons, produce a condition of coma 

 with unconsciousness. The question arises, Which of the many 

 active substances which possess this power are convenient and 

 suitable for use ? Careful observation has taught us that the 

 order of involvement of the various parts of the nervous sys- 

 tem by these substances the line of march of their phe- 

 nomena differs widely with the different drugs. With 

 some of them, such as Ether and Chloroform, the very first 

 phenomenon is disturbance of the convolutions ; and it is not 

 until consciousness has been completely removed, that any 

 serious depression of the medulla and its vital functions occurs. 

 With others, for example, Opium and Chloral, the cerebrum and 

 medulla appear to be simultaneously and equally involved; and 

 before consciousness has been completely removed, the centres 

 of respiration and circulation in the medulla may be dangerously 

 depressed. A third set of nervous depressants have hopelessly 

 paralysed the medulla before consciousness is much disturbed ; 

 such are Aconite and the irritant poisons. In selecting for use 

 a drug which will remove consciousness, we entirely reject the 

 third set. The first set, with Ether and Chloroform as their 

 types, we retain as our general anaesthetics ; the second set, 

 including chiefly Opium and Chloral, are used under special cir- 

 cumstances, and are generally called narcotics (vdpirri, a deep 

 sleep), or, as we have already seen, anodynes, pain destroyers. 



The action of narcotics is very complex, extending from one 

 extremity of the sensory side of the nervous system to the 

 other, influencing also its motor side, and disturbing the sensory, 

 motor, and metabolic functions of most of the viscera. In a 

 person under the full influence of Opium, an impression can only 

 be made with difficulty upon the peripheral nerves, or on the 

 organs of sense ; it is slowly and imperfectly conducted ; and it 

 is imperfectly perceived in the cerebrum. Thus cut off from 

 all but the most powerful external impressions, and itself 

 reduced in activity, the cerebrum is practically in the condition 

 of deep sleep, characterised by unconsciousness. A fact of 

 much greater importance, since unconsciousness is not of itself 



