506 EDWARD B. MEIGS 



work of Fahr^^ on the chemical constituents of the ash of frog's 

 striated muscle fibers confirms the view obtained by histological 

 examination. 



Histological examination of the preparations of smooth muscle 

 described above indicates that the muscle fibers occupy about 80 

 per cent of the volume of such preparations, the remainder being 

 made up of connective tissue and of interstitial spaces as in the 

 case of striated muscle. Thin cross sections of hving as well as 

 of fixed smooth muscle may be examined histologically, and the 

 proportional volume occupied by the fibers is about the same in 

 both the living and fixed preparations. 



It will be noticed that the striated muscle is prepared without 

 cutting across any of its fibers, while the fibers of the smooth mus- 

 cle preparations are cut across. A careful study of the effects of 

 cutting across the fibers of striated and smooth muscle has been 

 made. 



Rigor very quickly sets in in the neighborhood of a cut across 

 the fibers of striated muscle. If a frog's sartorius be cut across 

 its middle, and the two pieces be immersed in Ringer's solution, 

 whitish thickened areas make their appearance at the cut ends in 

 the course of a minute or so. These areas increase gradually in 

 size, so that at the end of perhaps four hours, the whole muscle is 

 shortened, opaque and unirritable. Another uninjured sartorius 

 used as a control may remain irritable for foxty-eight hours in the 

 same solution at the same temperature. 



Nothing of this sort occurs as a result of cutting across the 

 fibers of smooth muscle. I have cut sheets of smooth muscle 

 across in several places in such a way that the fibers had a length 

 of only 5 mm. between cubs. Such cut pieces of muscle have 

 been kept in Ringer's solution at about 20°, ^^ and their condition 

 has been compared with that of other pieces of muscle in which 

 the fibers had a length of 15 mm. between cuts. Both the con- 

 trols and the cut pieces of muscle often remained irritable for 

 forty-eight hours; the cutting made no differen.ce whatever in 

 the length of time which the tissue remained irritable, and there 



15 Fahr: Zeitschrift flir Biologic, 1908, Bd. 52, p. 80. 



" All temperatures are given in terms of the centigrade scale. 



