HYPOTHESIS OF VIBRATIONS. 117 



tangible shape, ingenuity was largely invoked in surmises regarding 

 their nature; and, generally, opinions settled down into the belief that 

 they were of an ethereal character. For the various views that have 

 been held upon the subject, the reader is referred to Haller, 1 who was 

 himself an ardent believer in their existence, and has wasted much time 

 and space in an unprofitable inquiry into their nature. The truth is, 

 that we have not sufficient evidence, direct or indirect, of the existence 

 of any nervous fluid of the kind described. Allusion has been already 

 made to the views, in regard to the tubular structure of the white neu- 

 rine, admitted by most observers: Berres, 2 affirms that the forms, which 

 the nervous substance assumes under the magnifying glass, can only be 

 compared to those of canals and vesicles; but whether they be hollow he 

 does not attempt to decide. M. Raspail 3 has concluded, that the opinion 

 of their being hollow, and containing a fluid, is unsupported by facts; 

 for although he admits, that M. Bogros succeeded in injecting the nerves 

 with mercury, he thinks that the passage of the metal along them was 

 owing to its having forced its way by gravity. Modern histologists 

 accord with great unanimity as to the tubular structure of the medullary 

 neurine ; but we have no reason for considering the brain the organ of 

 any ponderable secretion. Yet the term "animal spirits," although 

 their existence is not now believed, is retained in popular language. 

 We speak of a man who has a great flow of animal spirits, but without 

 regarding the hypothesis whence the expression originated. 



The term nervous fluid is still used by physiologists. By this, how- 

 ever, they simply mean the medium of communication or of convey- 

 ance, by which the nervous influence is carried with the rapidity of 

 lightning from one part of the system to another ; but without com- 

 mitting themselves as to its character ; so that, after all, the idea of 

 animal spirits is in part retained, although the term, as applied to the 

 nervous fluid is generally exploded. Dr. Good 4 directly admits them 

 under the more modern title ; Mr. J. W. Earle 5 firmly believes in the 

 existence of a circulation in the nervous system, and it is not easy to 

 conceive, that the brain does not possess the function of elaborating 

 some fluid, galvanoid or other, which is the great agent in the nerv- 

 ous function. 



2. The hypothesis of vibrations is ancient, but has been by no means 

 as generally admitted as the last. Among the moderns, it has received 

 the support of Condillac, 6 Hartley, 7 Blumenbach, 8 and others ; some 

 supposing, that the nervous matter itself is thrown into vibrations ; 

 others, that an invisible and subtile ether is diffused through it, which 

 acts the sole or chief part. As the latter is conceived, by many, to 

 be the mode in which electricity is transmitted along conducting wires, 



1 Elementa Physiologise, x. 8. 



3 Oesterreich. Med. Jahrbuch., B. ix., cksd in Brit, and Foreign Med. Review, January, 

 1838, p. 219. 3 Chimie Organique, p. 218. Paris, 1833. 



4 Study of Medicine, with Notes by S. Cooper, Doane's Amer. edit., vol. ii., in Proem to 

 Class iv. Neurotica, New York, 1835. 



5 New Exposition of the Functions of the Nerves, by James William Earle, Part. I. Lon- 

 don, 1833. 6 CEuvres, Paris, 1822. 



' Observations on Man, &c., chap. i. sect. 1. London, 1791. 

 8 Institutiones Physiologicse, 226. 



