Strychnia is thus an exciter of muscular contraction and of motion; exalting sensation in a less degree. It has also apparently some action on part of the ganglionic system of nerves, by which it is enabled to promote the function of the stomach, and becomes temporarily a tonic when given in relaxed conditions of that organ. But it does not excite the action of the heart.
In cases of poisoning by Nux Vomica, the brain and the heart are unaffected. Tetanic and general convulsions are produced; and the immediate cause of death is a spasm of the muscles of respiration.
Strychnia causes a contraction of the muscles by stimulating the motor centres, and originating in them an impulse which is propagated along the motor nerves. So that when these centres are diseased, or the continuity of their fibres destroyed, it is unable to exert its power. It is used as a medicine in cases of Paralysis. But when the lesion of the nervous centre is of recent occurrence, or when it has been of so serious or extensive a nature as to admit of no repair in the course of time, the remedy will be ineffectual. It is only successful in cases where the injury to the nervous centre has healed up, and where the limb continues paralyzed merely because the motor nerves have lost the power to transmit the necessary impulse, from having been so long unaccustomed to the discharge of this office.
As it is able to act on the nerve itself, it is sometimes thought best to apply it to the affected part on a raw surface produced by a blister. The advantage of this plan is most obvious in the case of Lead-palsy, where the cause of the paralysis is local, residing in the nerve, and not in the centre. But in this case also it is necessary that the nerve-centre be sound. Dr. Neligan recommends Strychnia in Lead-colic, in which disorder constipation and distention of the bowel are produced by a paralysis of a portion of the large intestine.
Strychnia has been used with benefit by Dr. Golding Bird in cases of Phosphaturia connected with a functional derangement of the spinal cord. (Vide p. 232.)
ALCOHOL
Class II. Div. II. Ord. I. Narcotica Inebriantia.
Class IV. Ord. V. Diaphoretica.
Class IV. Ord. VI. Diuretica.
We have already considered in order the peculiarities in action that distinguish Narcotics alike from Stimulant and Sedative medicines; how they tend first to exalt the nervous forces, and then to depress them, and have further a particular action on the intellectual part of the brain. We have observed that these remedies may be divided into three minor groups, which differ considerably, if only regarded in their action on the nervous forces generally. For that Inebriants approach very nearly to Stimulants, and Deliriants to Sedatives, while Soporifics occupy an intermediate place. We have seen also that though, during the stage of stimulation, these three orders tend all more or less to excite the powers of the mind, they differ characteristically in their secondary or depressing effect upon the same. That, with respect to our present purpose, the intellectual functions may be divided into three parts: the mind itself; volition and sensation, by which it is united to the body; and the special senses, by means of which it is connected with external things. And that the secondary or depressing action of Inebriants is such as to impair these three in a tolerably equal degree; that of Soporifics extinguishes for a time sensation, volition, and the five senses, while it may leave the mind unaffected; but that of Deliriants excites and deranges all the intellectual functions.