STRIATED MUSCLE. . 91 



these variations modify the form and energy of the contrac- 

 tions. The movement by which, at the moment when con- 

 traction takes place, the labor of muscular extension ceases, 

 is shown under the form of an increase of temperature. The 

 shortening is the effect of the peculiar and permanent elas- 

 ticity of the contractile spiral line ; the lengthening is pro- 

 duced by a moving cause which is developed in the act of 

 nutrition, and is correlative to heat, if it be not heat itself." l 



It seems certain, as we have already said, that we must 

 place the change of form of the muscle in the general class 

 of physiological phenomena. We know that one of the 

 essential properties of the globules is this power of change 

 of form : the muscular fibres are derived from the globules, 

 and have kept this property in a very striking degree, as well 

 as the other properties which we have already studied (elas- 

 ticity, electro-motor power, chemical changes, etc.) The 

 following experiment by Kiihne confirms this view of the 

 subject, by which, without offering any theory as to the phe- 

 nomenon, we at least include it among the general properties 

 of essentially living elements. By filling a fragment of the 

 intestine of an insect with protoplasm of the myxocimetes 

 (cryptogamous plants, composed only of extremely contrac- 

 tile globules of pure protoplasm), he formed an artificial 

 muscular fibre, having an envelope and contents, and present- 

 ing, under the action of excitants, all the appearance of a real 

 muscular fibre, that is to say, passing from the first to the 

 second form. 



As with the globules, however, it does not appear that the 

 change of form takes place at once in the whole extent of 

 the muscular fibre. If we examine a certain portion of a 

 fibre with the microscope, we find the change of form at first 

 local, and then spreading immediately, like a wave, along 

 the fibre. This experiment, which is easily made on the 

 muscles of insects, especially on the long slender legs of the 

 spider (in which the contraction of the muscular fibres may 

 be observed through the animal's transparent tissue), con- 

 firms what we have already quoted from Aeby and Marey 

 (p. 88), as to the muscular wave, as demonstrated by means 

 of the myographical pincers. 2 In it we make use, not of the 



1 Rouget, " Academic des Sciences," June, 1867. 



8 For an interesting, as well as instructive, account of the 

 changes of form of muscular fibre during contraction, as seen in a 

 muscle attached to a living animal, and viewed under the, micro- 



