22 O. LARSELL 
At intervals small bundles of fine fibers are given off from the 
main nerve trunks. These bundles pass to the muscle bands 
and there break up by the separation from them of the individual 
nerve fibers, as shown in figure 10. The individual nerve fibers, 
on reaching the muscle bands, divide into numerous slender 
filaments which run parallel between the muscle fibers, as illus- 
Fig. 10. Muscle bands in wall of a bronchus, illustrating the manner in which 
the nerve bundles break up into single strands and the manner in which these 
strands are distributed to the muscle fibers. Rabbit R4. Methylene-blue stain. 
60u. Camera lucida, stage level. X 150. 
trated in the figure, and at intervals give off short twigs, better 
shown in figure 11, which terminate near the nuclei of the indi- 
vidual smooth muscle cells, as already described. 
The recent work of Carlson and Luckhardt (’20) has demon- 
strated the presence of inhibitory fibers only, in the lungs of the 
axolotl and Necturus, while both inhibitory and motor fibers 
reach the lungs through the vagus nerve in the frog. .There 
appears to be an even larger number of motor fibers in the 
reptilian lung, as represented by the turtle. 
