90 NERVOUS SYSTEM. 



occur, which throw great difficulty on this matter. Two of the kind 

 have been related by Mr. Stanley and Dr. Budd, 1 in which there was 

 disease confined to the posterior column ; yet sensation remained un- 

 impaired, whilst the power of motion in the lower extremities was lost. 



Much evidently remains to be accomplished, before the precise 

 arrangement of the columns of the spinal cord, and of the relations of 

 the nerves connected with them, can be esteemed established. Sir 

 Charles Bell, 2 indeed, subsequently renounced his first opinion, that 

 the posterior roots of the spinal nerves proceed from the posterior 

 column, and described them as arising from the middle or lateral column ; 

 affirming, at the same time, that it is not impossible that the posterior 

 column may be connected with the sensitive roots of the spinal nerves, 

 although he has not hitherto succeeded in tracing it. Messrs. Grainger 

 and Swan maintain, that both sets are connected with the lateral columns 

 only; the anterior and posterior lateral fissures definitely limiting the 

 two roots. Perhaps, as suggested by Dr. Carpenter, 3 both these state- 

 ments may be too exclusive. The anterior roots would seem to have a 

 connexion with both the anterior and lateral columns ; and the posterior 

 cannot be said to be restricted to the lateral column, some of their 

 fibres entering the posterior division of the cord. 



Most physiologists are now of opinion, both from experiment and 

 reflection, that there is no special column destined for respiration, and 

 that there appears to be nothing so peculiar in the action of the respi- 

 ratory muscles, that they should require a distinct set of nerves. 4 



Sir C. Bell proposed a further arrangement of the nerves, more 

 natural and philosophical than the unmeaning numeration according 

 to the system of Willis, and better adapted to facilitate the com- 

 prehension of this intricate portion of anatomy. According to this, 

 all the nerves of the body may be referred to two great classes the 

 original, primitive or symmetrical, and the irregular or superadded. 

 It has been already remarked, that a division of the spinal cord has 

 been presumed to correspond to the cerebrum ; and another to the cere- 

 bellum. Now, every regular nerve has two roots, one from the anterior 

 of these columns, and another from the posterior. Such are the fifth 

 pair ; the sub-occipital ; the seven cervical ; the twelve dorsal ; the five 

 lumbar; and the six sacral, that is, thirty-two perfect, regular, or 

 double nerves, including, to state more briefly, all the spinal nerves, 

 and one encephalic the fifth pair. The fifth pair is found to arise 

 from the encephalon by two roots, and to have a ganglion upon the 

 posterior root. It is, accordingly, classed with the spinal nerves ; and, 

 like them, according to Sir Charles Bell, conveys both motion and sen- 

 sibility to the parts to which it is distributed. These regular nerves 

 are common to all animals, from the zoophyte to man. They run out 

 laterally; or in a direction perpendicular to the longitudinal division of 

 the body; and never take a course parallel to it. 



The other class is called irregular or superadded. The different 



1 Medico-Chirurgical Transactions, vol. xxiii., Lond., 1840. 



a Nervous System, &c., 3d edit., p. 234. London, 1836. 



3 Principles of Human Physiology, 2d Amer. edit., p. 125. Philad., 1845. 



* Dr. Reid, op. cit., Jan., 1838, p. 175. 



