194 



HISTOLOGY 



that seen in the innervation of some of the smooth muscle fibers of the in- 

 vertebrate animals. The leech has shown such an organ on some of the 

 muscle cells in the circular layer of muscle tissue in its body wall (Fig. 



FIG. 171. Stippled outline of part of a muscle fiber from the alimentary canal of the leech, 

 showing the end-organ of a motor nerve in contact with it. (From SCHNEIDER after APATHY.) 



171). Here the innervating fiber branches into simple and smooth divi- 

 sions that apply themselves to the body of the muscle cell. 



It has been questioned if these smooth terminal branches really rep- 

 resented the end-organs, and suggested that the real end-organs had failed 

 to take the stain, thus remaining invisible in the preparation. Huber 

 has found in the smooth muscle of the cat that the fibers do end in small 

 but distinct varicosities. 



FIG. 172. A, motor nerve end-organ on portions of two voluntary muscle fibers of Lacerta. 

 (From BOHM and DAVIDOFF'S Histology.) B, motor nerve end-organs on striated muscle 

 fibers of the frog. (After SIHLER in Zeits.f. wiss. Zool.) 



A more specialized motor nerve-ending on muscle can be seen in the 

 nerve-ending on amphibian muscle tissue (Fig. 172, B}. The motor 

 ending on the striated muscle fiber of the frog is branched into rather 

 long but decidedly thick and more irregular divisions. These show, 

 also, a feature characteristic of the more highly developed motor muscle 



