240 Mr. J. J. Woodward on the Modern 
simple amceboid movements of the protoplasm are the only 
movements; but in the higher forms, besides these, certain 
special contractile tissues make their appearance, by which 
the chief part of the mechanical work done is effected; these 
are the striated aud unstriated muscular fibres. 
On account of the extreme minuteness of the little proto- 
plasmic bodies in which the amceboid movements are mani- 
fested, the investigation of the mechanical means by which 
these movements are effected has not as yet been attempted, 
although a great mass of details have been accumulated by 
actual observation with regard to the phenomena themselves 
and the conditions under which they occur. Very little more 
has been done with regard to the contractions of the unstriated 
muscular fibres. The striated muscles, however, have been 
made the subject of a host of researches; and I suppose the 
conclusions to which we may ultimately be led by these can 
be regarded, with but little reservation, as applicable to the 
function of the unstriated muscles, and also to the simpler 
amceboid protoplasmic contractions. 
Yet, notwithstanding the vast amount of experimental 
labour and speculative ingenuity that has been lavished since 
the time of Haller upon the question of the contraction of the 
striated muscle, it must be confessed, in the honest language 
of Hermann *, that the problem still mocks our best endea- 
vours. Tor myself, I am unwilling to believe that the 
phenomena of muscular contraction, or, indeed, of any of the 
varieties of protoplasmic contraction by which animals effect 
mechanical work, will not by and by be fully and satisfac- 
torily explained on chemico-physical principles. I cannot for 
a moment give my adherence to the dogmatism of those 
modern vitalists who insist that the contractions of a muscle 
or of an Ameeba are essentially vital phenomena; for this 
would be to claim that life can create force. But it would be 
folly to shut our eyes to the circumstance that no chemico- 
physical explanation of muscular contraction yet offered has 
been so convincingly supported by facts as to command the 
universal assent of competent physiologists. 
Of the various hypotheses devised to explain muscular 
contraction, those which regard the phenomena as in some 
way resulting from electrical disturbances have long enjoyed 
great popularity. Such of these hypotheses as still survive 
are based upon the electrical manifestations actually observed 
in living muscles. It has been pretty generally accepted im 
accordance with the observations of Du Bois-Reymond, whose 
* 1. Hermann, Handb. der Phys. Bd. i. Th, 1, S. 242. 
