74 On tie intimate Structure of Muscular Fibre. [Xo. 1, 



rapid actions Which muscle is capable of effecting are accomplished, 

 it being kept in a state of perpetual tension depending on the action 

 of its spiral transverse bands. The most casual observer moreover 

 will at once perceive that through the mechanism I have endeavoured 

 to describe, no puckering or pinching of any of these delicate structures 

 can possibly occur, the parts being all admirably poised and adapted 

 to one another. 



Time will not permit me to extend this principle to the case of the 

 crystalline lens, but I am convinced that the lens is simply a mass of 

 contractile bands arranged in such a manner that in contracting and 

 dilating, the curve of its surfaces are capable of alteration, and its 

 refractive powers thus modified, so as to enable it to bring both parallel 

 and divergent rays of light to a focus on the retina. I cannot, however, 

 close this paper without alluding to the fact that the minute anatomy 

 of muscle I have delineated, evidently displays a source from whence 

 animal heat may be derived. I need hardly say that much of Liebig's 

 theory of the combustion of the hydrocarbons as being the chief if not 

 only source of animal heat is fast falling to the ground under the 

 assaults of modern chemistry. But in the action of a muscle, we have 

 evidence of the existence of forces as capable of engendering heat as 

 combustion, viz friction, compression, tension, and expansion,— they all 

 necessarily giving rise to molecular motion and an equivalent amount 

 of heat,— o x uite capable of keeping up the temperature of the blood to a 

 healthy standard, and this, by constantly circulating throughout the 

 body, would tend to equalize the temperature in all parts of the system. 

 Many distinguished physiologists have supposed that the nervous force 

 is analogous, if not identical, with electricity, and have pointed with 

 triumph to the evidence of the excitation of electricity during muscular 

 contraction; it appears to me, however, that we may easily explain the 

 presence of electricity by the play of the forces above enumerated 

 during muscular contraction : they must, in fact, induce electrical 

 phenomena, and that independently of the nervous system which is 

 simply the medium through which the mind acts. If therefore the 

 consideration of the minute anatomy of muscle is attended with no 

 other practical result, it serves to explain much that was before a 

 mystery in the animal economy. It has not advanced our knowledge 

 as to the influence which volition has over muscle, nor do I think 



