I 



CH. II.] EXTERNAL SENSATIONS. 37 



latter may be united to form larger trunks, as the spinal cord.^ 

 Further, at the place of origin of the nerve in the brain, there 

 is a distinct point where the material ideas must be developed 

 from the external impressions which it brings to the brain. 



40. It is useless to attempt an arrangement of the various 

 kinds of external impressions according to the variation in their 

 external sensations. Everything is ordered according to laws 

 altogether unknown, and which we can never fathom. Pain, 

 for example, is a sensation which usually arises from very 

 vehement external impressions on the nerves; nevertheless, 

 the most violent disturbance of a nerve is not always the most 

 painful. A corrosive fluid can excite a far more intolerable 

 pain in a nerve, than a blow which shatters the bone of the 

 limb. Neither is it the separation of the components of a 

 nerve by the corrosion, which causes the pain to be so acute, 

 for a sharp knife divides it without any remarkable pain. It 



' This important doctrine of the distinct course of each nerve-fibril was taught 

 at Leyden during the first half of the last century. The following quotation will 

 interest the reader : — '< The doctrine of Albinus, — indeed, of the whole school of 

 Boerhaave, — in regard to the nervous system, and, in particular, touching the dis- 

 tinction and the isolation of the ultimate nervous filaments, seems, during a century 

 of interval, not only to have been neglected, but absolutely forgotten ; and a counter- 

 opinion of the most erroneous character, with here and there a feeble echo of the 

 true, to have become generally prevalent in its stead. For, strange to say, this very 

 doctrine is that recently promulgated as the last consummation of nervous physiology 

 by the most illustrious physiologist in Europe. ' That the primitive fibres of all 

 the cerebro-spinal nerves are to be regarded as isolated and distinct from their 

 origin to their termination, and as radii issuing from the axis of the nervous 

 system,' is the grand result, as stated by himself, of the elaborate researches of 

 Johann Mueller; and to the earliest discovery of this general fact he carefully 

 vindicates his right against other contemporary observers, by stating that it had 

 been privately communicated by him to Van der Kolk, of Utrecht, so long ago as 

 the year 1830." (Phys., pp. 596-603 ; Supplementary Dissertations to Reid's Works, 

 by Sir W. Hamilton, Bart., &c., note D ; ' On the Distinction of the Primary and Se- 

 condary Qualities of Body,' p. 874.) 



This whole essay is a mine of suggestive thought to the neurologist, but is specially 

 interesting from containing a general abstract of the doctrines taught by the younger 

 Albinus, in his lectures delivered at Leyden, and which Sir W. Hamilton has obtained 

 from a manuscript copy in his Ubrary of the ' Dictata,' of Albinus, taken very fully 

 after the middle of the last century by Dr. William Grant, and collated with another 

 copy by an anonymous hand of 1741. Having, by the kindness of Sir William 

 Hamilton, had an opportunity of perusing a portion of these ' Dictata,' I cannot but 

 concur with that profound metaphysician in au expression of regret that they have 

 never been printed. — Ed. 



