8B4 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



senting themselves in far more rapid succession, and possessing a less perfect 

 mutual coherence. 



VIII. The foregoing states are closely allied to Insanity; many forms of which 

 may be almost exactly paralleled by transient states of Somnambulism, whilst 

 others are but a modification of Delirium. A deficiency or entire absence of the 

 controlling power of the Will is the common feature of all forms of this disorder, 

 and is frequently its first manifestation. But Insanity is essentially constituted 

 by excessive, deficient, or perverted activity of some one or more of the auto- 

 matic tendencies, and must thus be regarded as consisting in a disordered action 

 of the Cerebrum. This may be traced to a great variety of causes, which may be 

 classified in different ways, according as we take their own nature or their modus 

 operandi as the basis of our arrangement. Thus it is unquestionable that in a 

 large proportion of cases of settled Insanity, there is an impairment of the due 

 Nutrition of the Cerebrum; and this, which is often an hereditary defect, may' 

 arise de novo, like abnormal changes in the nutrition of other parts (CHAP. XI.), 

 from deficiency or perversion in the formative power of the tissue, or from an 

 imperfect supply, or from an altered character of its pabulum. Of the influence 

 of deficient or perverted formative power in the tissue, we have examples in the 

 Insanity resulting from mechanical injuries of the brain, and from excessive 

 "wear" of the organ by forced activity. Of the effects of deterioration in the 

 character of the blood, we have illustrations in the Insanity that is often linked 

 on with constitutional diseases of which such deterioration is a marked feature, 

 and in that which is so frequent a consequence of habitual excess in the use of 

 Alcoholic liquors. These conditions may exist in combination; 1 and it is, pro- 

 bably, by such a combination that many of the " moral causes" of Insanity 

 operate. For there can be little doubt that Emotional excitement, from its im- 

 mediate relation to Nerve-force ( 805), has a direct influence on the formative 

 capacity of the Cerebrum ; whilst, on the other hand, we know that it has so 

 great an influence over the Organic functions, that it can produce very serious 

 alterations in the condition of the Blood (CHAP. xvm). But without any serious 

 perversion of the nutrition of the Cerebrum, its action may be disturbed, either 

 by the presence of some toxic agent in the Blood, or by functional disturbance 

 in other parts of the Nervous system. The delirium of Intoxication is, whilst 

 it lasts, a true Insanity ; and it ceases because the poison is eliminated from the 

 system. But there are many cases in which there is a continual production of 

 a poison within the system, which deranges the normal train of mental action 

 so long as the blood is tainted by it ; the indication of treatment is here ob- 

 viously to check this production, and to depurate the blood ; and when this has 

 been effectually accomplished, the healthy action of the Brain is immediately 

 restored, which would not have been the case if its nutrition had been seriously 

 impaired. Most persons have experienced the extreme depression of spirits and 

 incapacity for mental exertion, which are consequent upon certain derangements 

 of the digestive function, and especially upon disorder of the biliary apparatus; 

 and it is unquestionable that many forms of Insanity, in which extreme dejec- 

 tion is a prominent symptom, but which may also include intellectual delusions, 



1 Thus Delirium tremens, which may be regarded as a form of temporary Insanity, essen- 

 tially consisting in perverted and imperfect nutrition of the Cerebrum, seems ordinarily 

 dependent conjointly upon the excessive and irregular activity to which the organ has been 

 previously forced, and on the alteration of the normal character of the Blood produced by 

 the habitual presence of Alcohol in its current ; but it is well known that Delirium tremens 

 may occur as the result of other agencies that primarily depress the nutritive power 

 without perverting the blood ; such as excessive depletion, the shock of severe injuries, or ex- 

 treme cold. In either case, however, the indications of treatment are the same ; namely, 

 to induce sleep, whereby the irregular activity of the organ may be completely suspended, 

 and its due nutrition restored : and to correct what may be faulty in the condition of the 

 blood. 



