244 Mr. J. J. Woodward on the Modern 
named inogen. During contraction inogen breaks down into 
carbon dioxide, lactic acid (Fleischmilchsiiure), and gelati- 
nous myosin. The rearrangement of molecules necessary to 
produce the latter body determines the contraction. Subse- 
quently the gelatinous myosin combines with the necessary 
materials furnished by the blood, and becomes inogen again. 
This decomposition and recomposition goes on also while the ~ 
muscle is at rest; but as then the gelatinous myosin is re- 
converted into inogen as rapidly as it is formed, no con- 
traction results. 
Du Bois-Reymond declares all this to be merely unsup- 
ported hypothesis *. Gamgee himself admits that it is after 
all not very clear why the gelatinous myosin should contract. 
Michael Foster ¢, who wholly rejects this particular chemical 
hypothesis, nevertheless seems quite sure that the true expla- 
nation will be found to be a chemical one. He insists that 
muscular contraction is essentially a translocation of molecules, 
and declares that whatever the exact way in which this trans- 
location is effected may be, it is fundamentally the result of 
a chemical change, or, as he describes it, ‘an explosive de- 
composition of certain parts of the muscle-substance.”’ 
The purpose I have in view does not require, fortunately, 
that I should attempt to decide whether these more purely 
chemical theories of muscular contraction or the more purely 
electrical theories are best entitled to confidence. My object 
has been effected if I have impressed you with the fact that 
wide differences of opinion still exist as to the nature of the 
process, and that further investigation is indispensable for the 
settlement of existing controversies. 
The subject thus briefly discussed brings us naturally to 
the consideration of the nature of the action of the motor 
nerves, by which, in all animals possessed of a muscular and 
nervous system, the contraction of the muscles is regulated 
and determined. 
The hypothesis which identifies the nervous currents with 
electricity was propounded in the posthumous work of Hausen} 
in 1748, and, notwithstanding all the difficulties and objec- 
tions it has encountered, still survives in a modified form in 
many contemporaneous minds. Those who hold to this view 
appeal in its support to the electrical phenomena actually 
observed in nerves in accordance with the investigations of 
* Du Bois-Reymond, Ges. Abh. Bd. ii. 8. 820, 
+ Foster, op. cit. p. 79 et seq. 
C. A. Hausen, ‘Novi profectus in historia electricitatis’ (Leipsic, 
1743). I cite from Du Bois-Reymond, ‘ Unters. ber thierische Elek- 
tricitat,’ Bd. ii. (Berlin, 1849), Th. i. 5. 211. 
