A MUSCLE-PRISM AND A MAGNET. 229 



But in all cases it must be borne in mind that these 

 are only theories, the value of which consists in the 

 very fact that they afford a common point from which 

 all the known facts may be regarded, and that they 

 must in no case contradict the value of scientifically 

 established facts. We require such hypotheses, partly 

 because they point the way to further research, and 

 thus greatly aid the advance of science ; and partly 

 because the human understanding finds no satisfaction 

 in the simple collection of separate facts, but rather 

 strives, wherever it has discovered a series of such 

 facts, to bring these, if only provisionally, into reason- 

 able connection, and to gain a common point of view 

 from which to regard them. 



3. Turning now to our task provided with these 

 preconceptions, we will at first confine our attention to 

 muscle. A regular muscle- prism exhibits a definite 

 distribution of tensions. But every smaller prism 

 which may be cut from the larger exhibits the same 

 distribution of tensions. No limits to this are as yet 

 known, for even the smallest piece of a single muscle- 

 fibre susceptible of examination is conditioned in this 

 respect just as a large bundle of long fibres. Two 

 possible explanations may be given of this. It may 

 be assumed that the electric tensions are due merely 

 to the arrangement of the muscle-prism, or such an 

 arrangement of electromotive forces already present 

 in the muscle may be conceived as explains all the 

 phenomena found to occur in the muscle. Mateucci 

 and others tried the first of these ways. But when 

 du Bois-Eeymond undertook the study of this subject, 

 and, with a degree of patience and perseverance un- 

 equalled in the history of science, discovered very many 



