184 STUDIES IN ELECTRO-PHYSIOLOGY: 



unipolar ; (3) voluntary muscles contract in parcels of 

 sarcomeres and not necessarily in one direction ; and (4) 

 cardiac muscles contract in" walls, " rhythmically, and as 

 the rate of propagation of the wave is slower than in 

 voluntary muscles, their inductive capacity, and possibly 

 their resistance, must be greater, probably by reason of the 

 conducting surfaces being connected, mainly if not en- 

 tirely, in parallel (see also p. 94). 



PLAIN MUSCLE 



In regard to plain muscle there is, as I have remarked 

 elsewhere, a lack of information. To my mind there can 

 be no manner of doubt that they are transversely striated, 

 although the striae are too small to be clearly observed. 

 I am forced to this conclusion by 

 several considerations, one of which 

 is that it is difficult to conceive how 

 they can shorten and broaden if only 

 longitudinally striated. They would 

 flatten but not shorten. Professor 

 Rosenthal says : "It must be observed 

 that the distinction between striated 

 and smooth muscle-fibres is not abso- 

 lute ; for there are transitionary forms, 

 such^ as the muscles of molluscs. The 

 latter consist of fibres, exhibiting to 

 some extent a striated character, and, 

 in addition to this, the character of 

 double refraction. At these points 

 the disdiaclasts are probably arranged 

 regularly and in large groups, while at 

 other points (as in true smooth muscle- 

 fibres) they are irregularly scattered and are therefore not 

 noticeable." 



Fig. 95. MUSCULAR 



FIBRE-CELL FROM THE 



MUSCULAR COAT OF 



THE SMALL INTESTINE. 



(After Schafer.) 



