RECAPITULATION AND PATHOLOGICAL APPLICATIONS. 221 



where convulsions present themselves during diseases which appear limited 

 to the Brain, we may infer that one of these systems is involved. Dr. M. 

 Hall has recently pointed out, that this complication is due to the impressions 

 made upon the fibres of the Spinal nerves distributed upon the Dura Mater, 

 and other serious and fibrous membranes ; for convulsive actions may be in- 

 duced by pinching these membranes, or otherwise irritating them. Of the 

 distinct forms or combinations, of which the class of convulsive disorders is 

 composed, Tetanus is one of the most interesting and instructive. This disease 

 is evidently dependent upon a state of undue excitability of the whole Spinal 

 System ; and this may be produced by different causes. That which is 

 termed the idiopathic form of the disease has its origin in the centres ; it may 

 result in Man from the operation of various predisposing and exciting causes ; 

 and may be artificially induced in Animals by the administration of Strychnia. 

 In the traumatic form of the disease, the morbid state has its origin in a local 

 injury; and the irritation propagated from this, and operating through the 

 Spinal Cord, may be itself a cause of many of the convulsive movements. 

 But, when the irritable state is once established in the nervous centres, con- 

 vulsive action of the muscles may be excited by any stimuli, and even almost 

 entirely without external causes. Hence it is that, whilst the amputation of 

 the injured part is not unfrequently the means of saving the patient, if per- 

 formed sufficiently early, it is attended with no benefit if delayed. The 

 Cerebral apparatus is entirely unaffected in this disorder ; but the nerves of 

 deglutition are usually those first influenced by it ; those of respiration, how- 

 ever, being soon affected, as also those of the trunk in general. The condition 

 termed Hydrophobia is nearly allied to that of traumatic Tetanus, differing 

 chiefly in the mode in which the cerebro-spinal axis is affected. The irritable 

 state of the nervous centres results from a local injury of a peculiar kind; and 

 here, too, the early removal of the part is very desirable as a means of pre- 

 vention ; although, when the malady has once reached the centres, it is of no 

 use. The muscles of respiration and deglutition are, as in Tetanus, those 

 spasmodically affected in the first instance ; but there is this curious difference- 

 in the mode in which they are excited to action, that, whilst in Tetanus the 

 stimulus operates through the true Spinal Cord (either centrally, or by being 

 conveyed from the periphery), in Hydrophobia it is often conducted from the 

 ganglia of special sense, or even from the brain ; so that the sight or sound of 

 fluids, or even the idea of them, occasions equally with their contact, or with 

 that of a current of air the most distressing convulsions. It would seem 

 therefore, as if the Emotional system of nerves was involved in it. 



299. Epilepsy is another convulsive disease, principally involving the Spinal 

 Cord, but partly affecting the Brain. The predisposition to convulsive move- 

 ments may depend upon many causes ; but the movements themselves are in 

 general immediately excited by some local irritation, as by the presence of undi- 

 gested matter in the stomach, of worms in the intestines, &c., although fre- 

 quently also from causes purely mental. The convulsive movements usually 

 affect the muscular system very extensively ; acting especially upon the mus- 

 cles of ingestion and egestion. The Brain is evidently much concerned in the 

 disease, however; as is evident from the numerous instances in which it has 

 been clearly traced to some local affection of that organ, as well as from the 

 loss of consciousness which accompanies the convulsion. Many forms of that 

 protean- malady, Hysteria, are attended with a similar irritability of the Ner- 

 vous Centres ; but there is this remarkable difference in the two cases, that 

 the morbid phenomena of Hysteria, whilst they often simulate those of Teta- 

 nus, Hydrophobia, Epilepsy, &c., are evidently dependent upon a state of the 

 system of -a much less abnormal character, being relieved by very mild reme- 

 dies, and being often capable of prevention by a strong effort of the will. Dr. 



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