io 4 SCIENCE PROGRESS 



1815 when he imagined a "circulation in the nervous system 

 from and to almost every point of the body, ascending to the 

 cerebrum by a nerve of sensation and returning by a nerve of 

 volition." 



That Walker in 18 15, i.e. before Magendie's discovery of 1822, 

 pictured the sensory direction as up the anterior and the motor 

 direction as down the posterior parts of the circuit does not in 

 any way obscure the idea of the nervous circuit. What Bell 

 added to this idea in 1826 was the specific picture of a muscular 

 circuit, by sensory nerves from muscle to brain and by motor 

 nerves from brain to muscle. 



Bell's sixth paper (1829) — his second paper on the nerves of 

 the face— is a revised and greatly improved edition of his first 

 paper of 1821. The improvements are entirely consequent upon 

 the distinction made by Magendie between motor and sensory 

 nerves and upon the experiments published by Mayo on the 

 nerves of the face ; they are also in part due to Bell's better 

 understanding of the anatomy of the fifth nerve as described in 

 Bellingeri's thesis of 1818. Both in the text and in accompany- 

 ing figures the essential points as regards the physiology of the 

 spinal roots and of the two parts of the fifth nerve are clearly 

 and correctly given. Assuredly if this second paper of 1829 

 had been written in 1821, Bell's title to the discovery of the 

 distinction between the motor and sensory functions of the 

 spinal roots and of nerves in general would have been clear. 

 But as a matter of fact the paper contains no additional results 

 of Bell's work, the improvements are in substance due to the 

 incorporation of the results obtained by Magendie and by Mayo 

 in 1822 and 1823. 



By the sixth paper Bell has returned to his point of departure 

 and completed the circle of his most active period of physio- 

 logical publication. After 1829 there is nothing further from his 

 pen worth mentioning ; three further papers appeared indeed in 

 the Phil. Trans, of the Royal Society, in 1832 " On the Organs of 

 the Human Voice," in 1834 and in 1835 "On the Functions of 

 some parts of the Brain " and " On the Relations between the 

 Nerves of Motion and of Sensation." After 1836 when Bell 

 returned to Edinburgh as Professor of Surgery, several short 

 papers from him " On the Nerves " were communicated to the 

 Transactions of the Royal Society of Edinburgh. None of these 



