OPIUM. 189 



2. ACTION ON THE BLOOD. 



Morphia enters the circulation less quickly than some 

 other alkaloids, although the first traces of the drug are 

 rapidly discovered in the blood. Thus its full action is 

 comparatively slowly developed, and solid opium continues to 

 exert local effects even in the colon, portion by portion of the 

 morphia being absorbed into the vessels. The red corpuscles 

 are said to be reduced in size indirectly, possibly through 

 slowing of the circulation and want of oxygen. 



3. SPECIFIC ACTION. 



After administration morphia may be found in all the 

 organs, which, probably without exception, are physiologically 

 affected by it; but its principal action is exerted upon the 

 nervous system. 



The convolutions are first briefly excited, and afterwards 

 depressed, probably by direct action of the morphia upon the 

 nerve-cells, not on the cerebral vessels. The stage of opium 

 excitement transcends even the first stage of alcoholic intoxica- 

 tion in the exaltation of feelings, the sense of happiness and 

 comfort, the brilliancy of imagination, and the increase of in- 

 tellectual power and mental vigour generally, all accompanied 

 by brightness of expression and manner. But the effect of 

 opium, even in this stage, is rarely one of pure exaltation, and 

 in most persons is perhaps never so. There is generally some 

 perversion of the faculties, and the imagination becomes extra- 

 vagant, wandering into the land of dreams, of the grotesque, 

 and the impossible. Depression now supervenes : the various 

 perceptive and sensory centres in the convolutions are more or 

 less depressed, according to the dose ; impressions made upon 

 the afferent nerves, including pain, do not readily affect the 

 receptive centres ; the subject becomes drowsy, and finally 

 ; and if he momentarily respond to a sharp enquiry or 

 other forms of stimulation, he quickly relapses into heavy 

 sopor. If the dose has been excessive, the stage of excitement is 

 entirely absent, the cerebrum is speedily and profoundly de- 

 pressed, and no response follows severe forms of stimulation, 

 such as flagellation : the patient is comatose. These effects of 

 opium on the brain as a stimulant, hypnotic, anodyne, and 

 narcotic, are more marked in man and in highly intellrrtu.il 

 races than in animals and lower races respectively. In cold- 

 blooded animals they are quite subordinate to the effects of 

 stimulation of the cord. 



The ganglia at the base of the brain are affected by opium, 

 en using contraction of the pupil, and disturbance of accom- 

 modation. 



