268 VEGETABLE DRUGS 



In diminishing both secretion and motion, opium causes constipa- 

 tion in health, but is most useful in relieving vomiting and diarrhea. In 

 toxic doses, opium may induce diarrhea, and this almost invariably occurs 

 after large doses of morphine subcutaneously (gr. i.) which the author 

 uses in preparing dogs for operation under ether — when little of the latter 

 is required. This action may be due to stimulation of the intestinal 

 muscle. 



Blood and Elimination. — After morphine has been injected under 

 the skin of a dog it may be found in the mouth and stomach within a 

 few minutes. Some 30% is eliminated by the stomach, and nearly 40% 

 by the feces. It is probably reabsorbed and resecreted in the digestive 

 tract. Traces are found in the milk, sweat and urine, while that re- 

 maining in the body is oxidized into the innocuous oxydimorphine. Mor- 

 phine wholly disappears from the body in two days. 



Nervous System. — The most important action of opium is exerted 

 upon the nervous system. It is necessary to study the drug from the 

 comparative standpoint in order to obtain a full understanding of its 

 effects. The brain of man, being more highly developed and sensitive, 

 in comparison with other parts of the nervous system, than the brain of 

 the lower animals, it follows that this organ is more powerfully in- 

 fluenced in man, while the spinal cord is often mainly impressed in the 

 lower animals. 



We may take the action of opium on the frog, at one end of the 

 scale, as exhibiting the most active spinal symptoms; while in man, at 

 the other end of the scale, cerebral phenomena predominate. The other 

 animals occupy an intermediate position; the action upon the horse and 

 ruminants is something between that exerted upon the frog and man, 

 andthe influence upon dogs approaches more nearly that seen in human 

 beings, only that a relatively greater dose is required to produce the 

 same result, as the brain is not so highly organized or sensitive to the 

 action of medicines. The brain of the horse is only one-twelfth as large 

 as that of man, in proportion to their respective body weights, and it 

 follows that the spinal cord of the horse is more readily affected by 

 opium, in accordance with the general law that the more highly devel- 

 oped a part is, the more easily is it influenced by therapeutic agents. 



Opium exerts first a stimulating, and then a depressing action upon 

 the brain and spinal cord, and in studying the action comparatively it 

 will be noted that the influence upon the cord in the frog, horse, Rumi- 

 nant, and to some extent in the dog, preponderates frequently over the 

 effect of the drug upon the brain, for the reasons stated above. 



^^Action on the Frog. — In non-poisonous doses, sleep is produced and 

 diminished spinal reflex activity, followed by a period of reflex excite- 

 ment. Toxic doses of 1 or 2 grains of morphine, injected under the 

 skin, cause at first a condition where convulsions occur, if the animal 

 is artificially irritated; later they come on spontaneously. This state is 

 followed by general paralysis, respiratory failure and death. The con- 

 vulsions are shown to be due mainly to stimulation of the receptive and 

 transmitting cells of the spinal cord, as in strychnine poisoning. 



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