On Muscular Motion and Animal Spirits 235 



swells as to breadth, but becomes less as to length ; 

 and in this way a muscle can be shortened, although 

 its fibres suffer no contraction. 



But whether a change of this kind takes place in a 

 muscle, and its contraction depends on this alone, I 

 shall not say for certain. Still, it does appear to me 

 that a contracted muscle does not swell up so much as 

 would be required if its contraction were caused in 

 this way. Besides, I do not see what part of the 

 muscle should sustain the attack of the motive matter 

 in such contraction, for some kind of membranous 

 vesicles, rather than muscular cords, would be suitable 

 for bearing the force of contraction, and yet the 

 strength of a muscle seems to proceed from its fibrils 

 and cords rather than from any kind of vesicles or 

 membranes. But these things will be discussed more 

 fully below. 



CHAPTER II 



A SHORT DESCRIPTION OF MUSCLES. ALSO WHAT 

 PART OF A MUSCLE PRIMARILY CONTRACTS 



In the anatomical dissection of muscles the first thing 

 that presents itself is a membranous integument spread 

 in all directions over each muscle ; under which come 

 into view series of fleshy fibres ; these, parallel among 

 themselves, are inserted obliquely into the opposite 

 tendons, which are parallel one to the other, as the 

 eminent Steno first observed. 



Next, there come to view the wonderful series of 

 almost infinite membranous fibrils, which, parallel 

 among themselves, cut the fleshy fibres obliquely, for 



