discovery; and it furnished Bell himself with the means of correcting his original views, and of arriving at his great discovery, before it was adopted by any one else. For there is ample evidence that between 1812 and 1821, Bell had been led by his experiments to adopt the conclusion, that the anterior roots of the spinal nerves are subservient to motion, and the posterior to sensation, respectively; the motor and sensory fibrils being essentially distinct, although bound up in the same trunks and branches, and having different terminations, both in the central organs from which they issue, and in the peripheral parts to which they are distributed. This conclusion was explicitly announced both by himself and by Mr. John Shaw, in their anatomical lectures at the Windmill Street school. Seeing, however, that the nerves of the head afforded peculiar facilities for working out the details of this doctrine, Bell gave his special attention to them; and having also conceived the idea that the nerves of respiration and of expression proceeded from a distinct tract in the medulla oblongata (the upper portion of the spinal cord, which lies within the cranial cavity), the first memoir communicated by him to the Royal Society did not develope what is now estimated as his fundamental discovery, but was chiefly devoted to an examination of the respective functions of the fifth and seventh pairs of cranial nerves. In this memoir the analogy of the fifth pair to the spinal nerves, in virtue of its two sets of roots, and of the ganglion upon the larger (sensory) root, is explicitly pointed out; and it was shown by experiment to be a nerve of double function. Bell was not acquainted, however, with the fact which had been ascertained by previous anatomists, that the fibres proceeding from the smaller (motor) root are distributed only to the third of the three principal divisions of the nerve, so that the first and second divisions, which are distributed to the upper part of the face and head, are exclusively sensory, while the third, which is alone possessed of motor as well as sensory endowments, is limited in its distribution to the muscles of mastication. This correction was speedily supplied by the experimental inquiries of Magendie and Mayo; and it is not altogether to the credit of Sir C. Bell, that, in the later reprints of this memoir, he adopted the correction, without any intimation of the source from which it had been derived. With regard to the functions of the seventh pair, Bell maintained (as Willis had done before), that it was essentially motor; but he considered its motor action to be limited to bringing the muscles of the face into co-operation in the respiratory function, and to exciting the movements of expression. Here, again, subsequent research has proved that he was in error; the seventh pair being the ordinary motor nerve of the face, and the movements of respiration and of expression being only particular modes of its general action. Physiologists, in fact, have long perceived that Sir C. Bell was in error in endeavouring to isolate the movements of respiration from the other "sympathetic" or (as they are now called) "reflex" actions with which they had been previously associated; and no one has any doubt that the movements of expression or emotion are performed through the same nervous channel as the movements of volition, although having a different source in the central organs. It is not a little remarkable that this part of Sir C. Bell's system was the one on which he especially prided himself; and that to the end of his life he continued to uphold it, professing his inability to understand the doctrines of "reflex action," which were then being pressed on the attention of physiologists by Dr. Marshall Hall and his followers.
The subsequent labours of Sir C. Bell on the nervous system were directed to the confirmation and extension of his doctrines, both by anatomical research, by experimental inquiry, and by pathological observation. He successfully demonstrated the course of the sensory and motor tracts ascending from the spinal cord to enter the brain, and showed how roots of the cranial nerves are connected with one or the other, or with both, according as they are exclusively sensory, or exclusively motor, or of mixed endowments. He attempted also to show that the anterior and posterior portions of the spinal cord have endowments corresponding with those of their nerves; but this conclusion, though at first generally accepted, has been rendered more than doubtful, both by the results of experiment and by the phenomena of disease. Under the title of the "Nervous Circle," he developed, more fully than had been previously done, the importance of "guiding sensations" in all voluntary movement; these sensations being usually derived from the muscles themselves, but being replaced by those of some other kind (as sight) when the "muscular sense" (which he considered to be a peculiar form of sensation, different from ordinary touch) is deficient. And in various parts of his memoirs, he threw out most important hints as to the rational interpretation of symptoms, and the application of remedies, which give them a high practical value.
Notwithstanding that Sir Charles Bell's method of investigation did not always conduct him to the truth, and his results had to be corrected by the labours of others, yet it is impossible for it ever to be forgotten that by him was laid the sure foundation of all subsequent knowledge of nervous physiology, in the discovery of the respective functions of the anterior and posterior roots of the spinal nerves, and in the general doctrine to which that discovery led, of the distinctness of function of each individual fibril, in virtue alike of its central and of its peripheral connections.—W. B. C.
BELL, Henry. This ingenious mechanic, the first in Europe who successfully applied steam to the purposes of navigation, was born in 1767 at Torphichen in Linlithgowshire. He was descended from a race of mechanics, some of whom enjoyed more than local fame. After receiving a scanty education at the parish school of Torphichen, he was apprenticed to a stonemason in 1780, but shortly after exchanged that craft for that of a millwright. At the expiry of his engagement he went to Borrowstounness to be instructed in ship-modelling, and in 1787, for the purpose of improving himself in mechanics, engaged with Mr. Inglis, engineer, at Bell's Hill. With the same purpose in view he found his way to London, and was for some time in the employment of the celebrated Rennie. Returning to Scotland about the year 1790, he established himself at Glasgow, and, either from want of capital or from want of perseverance, failing in his views of becoming an undertaker of public works, laboured as a common house-carpenter. The records of the corporation of wrights in Glasgow mention that he was entered a member of that body, October 20, 1797. In 1808 he removed to Helensburgh on the frith of Clyde, then an inconsiderable village, and pursued at leisure his multifarious mechanical schemes, or rather projected innumerable novelties in mechanics, which, with characteristic inconstancy, were successively abandoned; while his wife, who possessed in a remarkable degree the steady industry which her husband lacked, managed with profit the Baths' Inn, a large and much-frequented establishment. After engaging with infinite zest and grievous loss in a variety of projects, either totally impracticable or much beyond his means and the range of his scientific acquirements, his attention was directed by the experiments of Miller of Dalswinton to the subject of steam navigation. Miller's experiments, like Fulton's in America and others previously made in France, had demonstrated the possibility of applying steam to the purpose of navigation, but no practical success had as yet attended any attempt in Europe to introduce steam vessels. It was reserved for Henry Bell to accomplish this important object. He constructed in 1812 a vessel forty feet in length, which propelled by paddles in the way now so commonly known throughout the world, was found capable of making way against a head-tide in the river at the rate of seven miles an hour. This small craft for some months, until dwindled in the public estimation by larger vessels for which, without profit to the inventor, it served as a model, was a wonder of the nation under the name of the Comet; and if the gigantic results which have followed its success could have been instantly foreseen, it is possible that the surprise of his countrymen might have been taken advantage of to recognize, in some suitable way, the claims of Henry Bell. As it was, the public handsomely allowed him to do the best he could with his invention, did him the honour of adopting it, and left him until late in life, a prey to fears of starvation, which were by no means unreasonable. He was latterly in some measure relieved of embarrassments which weighed heavily on his mind by the kindness of some friends, especially in Glasgow, who interested themselves in raising subscriptions for his benefit. A grant of £200 by government, and an annuity of £100 from the trustees of the river Clyde, were afterwards added to these acknowledgments of the gratitude which this remarkable man claimed from his countrymen. He died at Helensburgh in 1830. A half of the annuity was continued to his widow. Attempts were made during his lifetime, and renewed after his death, to discredit his claims as an inventor, and it was plausibly urged that Fulton's steamer having plied on the
