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IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
well as isolated ganglion cells (multipolar and bipolar) along the 
course of the main vago-sympathetic nerve trunks on the surface 
of the lung, the nerve fibers of which are both medullated and non- 
medullated. In addition, there is a plexus of fine non-medullated 
nerve fibers which surrounds the strands of the lung musculature. 
These nerve plexuses and ganglion cells are most abundant at the 
base of the lung and Arnold points out that these are histologically 
identical with those of the frog’s heart. They are also probably 
identical, both as to histology and function, with the ganglionic 
plexuses (Auerbach) in the wall of the gut, especially as the 
lung is a diverticulum from the foregut (esophagus), therefore, it 
would be reasonable to look for a gradual physiological readjust- 
ment of the peripheral lung motor mechanism similar to that which 
gradually occurs in the case of the gastro-neuromuscular mechan- 
ism of the bullfrog (6) after section of the vagi or the splanchnic 
nerves. 
Fig. 31a. Frog 10, control, showing the normal contour of the flanks. (After 6 
we«ks as a control animal bilateral vagotomy was performed. It then lived 247 
days and was the only animal in which complete physiological readjustment of the 
peripheral lung motor mechanism occurred.) 
