114 O. LARSELL 
is represented as translucent, as it appears in a balsam mount, 
so that the nerve fiber shows through it. The fiber pursues a 
tortuous course outside the epithelial wall of the bronchiolus 
to the point where the latter divides to give rise to the alveolar 
ducts. At this point, between the openings into the alveolar 
ducts, there is a nodule of somewhat thickened epithelium. 
The nerve fiber enters this nodule and breaks up into numerous 
fine branches, each of which terminates as a small knob. All 
the twigs, as well as the entering fiber, have numerous vari- 
cosities. 
This same termination is represented at greater magnification 
in figure 6, in which the details of structure are more clearly 
shown. As represented in the figure, a central filament may be 
followed for a considerable distance. This filament gives off 
the numerous branches to which reference has already been made. 
These branches interlace in the most confusing manner. Many of 
them subdivide into smaller rami which terminate in minute 
knobs. The larger mass near the center of the figure indicates 
a varicosity of unusual size, which is somewhat foreshortened 
in the figure, and on that account appears larger than it does 
in the preparation itself. 
The terminal fibers in the two terminations last described, 
and in numerous others which were observed to occupy a corre- 
sponding position, are curved, as already noted, and appear 
somewhat drawn together, in contrast with the extended and 
radiating ultimate processes of those previously described. 
Whether or not this difference is of significance is problematical. 
The suggestion presents itself that these terminations located 
at the openings into the respiratory portion of the lung may 
represent a somewhat different functional type than those 
located in the larger air passages. It appears possible that the 
latter represent a type of tactile terminations which may be 
stimulated by foreign bodies or by masses of mucus within the 
bronchi. ‘Their location at the portals to the smaller-air passages 
appears admirably adapted to guard against the entrance of 
such objects from the larger bronchi by causing stimulation at 
the points such objects would naturally strike, and thus produc- 
