CH. VI.] 



CAKDIAC AND PLAIN MUSCLE 



frequent intervals by short branches (fig. 86). The fibres are smaller 

 than those of the ordinary striated muscles, and their transverse 

 striation is less distinct. No sarcolemma 

 can be discerned. Each fibre has only one 

 nucleus which is situated in the middle of 

 its substance. At the junctions of the 

 fibres there is a certain amount of cement- 

 ing material, stainable by silver nitrate. 

 This is bridged across by fine fibrils from 

 cell to cell. 



The above is a general description of 

 the fibres in the great mass of the oardiac 

 musculature. But immediately beneath 

 the lining membrane of the ventricles, 

 and in the main connecting strand which 

 links the auricles to the ventricles (the 

 auriculo-ventricular bundle) are found 

 peculiar fibres known after their discoverer Fl - se. Muscular fibre-ceils from 



, . . , , the heart. (E. A. Schafer.) 



as PurkiTije s fibres ; these are large, clear, 



quadrangular cells with granular protoplasm containing several nuclei, 

 and striated only on their margins. The special meaning and 

 function of these fibres will be described in the chapter on the heart. 



FIG. 87. Muscular fibre-cells from the muscular coat of intestine highly magnified. Note the longi- 

 tudinal striation, and in the broken fibre the sheath is visible. 



Plain Muscle. 



Plain muscle forms the proper muscular coats (1.) of the digestive 



