196 



SGIEN'CE. 



[Vol. VIII., No. 186 



lectual faculties of the highest order, such as 

 none of his descendants have surpassed. His 

 speech, we may be sure, was not a mere mumble 

 of disjointed sounds, framed of interjections and 

 of imitations of the cries of beasts and birds. It 

 was, like every language now spoken anywhere 

 on earth by any tribe, however rude or savage, a 

 full, expressive, well-organized speech, complete 

 in all its parts. The first men spoke, because 

 they possessed, along with the vocal organs, the 

 cerebral faculty of speech. As Professor Max Miil- 

 ler has well said, "that faculty was an instinct 

 of the mind, as irresistible as any other instinct." 

 It was as impossible for the first child endowed 

 with this faculty not to speak, in the presence of 

 a companion similarly endowed, as it would be 

 for a nightingale or a thrush not to carol to its 

 mate. The same faculty creates the same neces- 

 sity in our days ; and its exercise by young chil- 

 dren, when accidentally isolated from the teach- 

 ings and influence of grown companions, will 

 readily account for the existence of all the diver- 

 sities of speech on our globe. 



WHAT IS NERVE -FORCE 9 



A DISTINGUISHED biologist has remarked, with 

 great truth, that the study of the nervous system 

 is the true field of battle for physiologists, all 

 other investigations, however interesting and im- 

 portant, being of the nature of skirmishes, pre- 

 paratory for and surely leading up to the final 

 conflict, in which we must engage before we can 

 hope to gain a position from which nature's most 

 mysterious processes are laid bare to our view. 

 Of all the functions of the nervous system, the 

 one which, at first sight, would seem most acces- 

 sible to investigation, is that of the nerve-fibre 

 itself. What conception can we form of the 

 physical or chemical changes which take place in 

 those white glistening bands which are for us the 

 only channels through which knowledge of the 

 physical universe can be obtained, and which also 

 enable us to impress upon the world around us the 

 evidence of our conscious personality? 



With the discoveries of Du Bois Reymond, the 

 hope arose that nerve-activity might be explained 

 as an electrical phenomenon, and the attempts 

 made to build up a satisfactory electrical theory 

 of nervous action have been numerous and in- 

 genious. The important facts which forbid the 

 identification of nerve-force with electi'icity are : 

 the absence of an insulating sheath on the nerve- 

 fibre, the slow rate at which the nerve-force is 



Abstract of an address before the section of biology of 

 the American association for the advancement of science 

 at Buffalo, Aug. 19, 1886, by Dr. H. P. Bowditch, of Boston, 

 Mass., vice-president of the section. 



transmitted, and the effect of a ligature on a 

 nerve in preventing the passage of nerve-force, 

 while not intei'fering with that of electricity. 

 The electrical phenomena connected with the 

 functional activity of nerves (action-current, elec- 

 trotonus) appear, therefore, to be secondary in 

 their character, and not to constitute the essential 

 process in nerve action. In this connection should 

 be noted an experiment of d'Arsonval,^ which 

 shows how the electrical phenomena associated 

 with the activity of nerves may be imitated by 

 purely physical means. This observer filled a glass 

 tube, of one or two millimetres interior diameter, 

 with drops of mercury alternating with drops of 

 acidulated water, thus forming a series of capil- 

 lary electrometers. The tube was closed at its 

 two ends with rubber membranes, and was pro- 

 vided with lateral openings by which its interior 

 could be connected with electrical conductors. 

 A blow upon one of the membranes caused an 

 undulation of the liquid column, which was prop- 

 agated from one end to the other of the tube, 

 and was accompanied by a wave of electrical 

 oscillation, which was propagated at the same 

 rate. The phenomenon is, according to d'Arsonval, 

 to be explained as follows : The blow upon the 

 membrane changes the form of the surface of 

 contact between the first two cylinders of mercury 

 and acidulated water. This change of form is 

 transmitted to the following cylinders with a 

 rapidity dependent upon the nature of the fluid. 

 But each of these changes of shape is accom- 

 panied by the production of an electric current 

 (Lippmann's phenomenon, due to variation of 

 superficial tension), and the tube is therefore trav- 

 ersed by an electric wave, which necessarily has 

 the same rate as the undulation of the liquid 

 column. The analogy between this phenomenon 

 and the wave-like propagation of the action-cur- 

 rent in nf^rves is sufliciently obvious. 



In studying the nature of nerve- force, two alter- 

 natives present themselves. We may conceive 

 the impulse to be conducted through the 

 nerve-fibre by a series of retrograde chemical 

 changes in the successive molecules of the nerve- 

 substance, the change occurring in one portion of 

 the fibre acting to produce a similar change in 

 the neighboring portion. As this process is as- 

 sociated with the using up of organic material, 

 and the consequent discharge of potential energy 

 in the successive portions of the nerve, the theory 

 maybe called ' the discharging hypothesis.' The 

 burning of a line of gunpowder may be taken as 

 an example of this sort of action. On the other 

 hand, we may conceive that the nerve-force is 

 transmitted from molecule to molecule by some 

 1 Comptes rendus soc. biol., April 3, 1886. 



