JAMES D. HARDY 
329 
ly there were no visible lymphatic vessels, it 
was evident that the adjacent pair of hilar 
lymph nodes were stained within 45 minutes. 
By the 12th postoperative day not only were the 
adjacent lymph nodes stained, but also a few 
small lymphatic vessels were visible running 
across the bronchial anastomosis. By the 20th 
day, many stained lymphatic vessels could be 
demonstrated crossing the suture line and en- 
tering the peribronchial lymph nodes, and some 
of these channels coursed directly to the trachea. 
Furthermore, the newly regenerated vessels 
were almost as large as those seen in the normal 
lung. Incidentally, we found that the lymphatic 
channels were restored as readily in the al- 
lotransplanted lung as in the replanted lung. 
At that particular time in the course of our 
long-term investigation of lung transplantation, 
we concluded that the regeneration of lympha- 
tics might play a significant role in the dissipa- 
tion of the pulmonary congestion which usually 
followed replantation of the lung. The regenera- 
tion of lung lymphatics had of course been 
studied by others in the past. 
Nerve Regeneration Following Lung Replantation 
It was long believed that the innervation 
of the major bronchi was essential to pro- 
vide adequate respiratory reflex drive, and 
thus the capacity of pulmonary nerves to 
regenerate was accorded considerable investiga- 
tion in the early years of lung replantation stu- 
dies.27-30 Parenthetically, it may be noted here 
that it has been shown by simultaneous bi- 
lateral lung replantation that the pulmonary 
nerves are not essential for adequate respira- 
tory function, though it would be misleading 
to imply that pulmonary innervation is not im- 
portant in achieving normal efficiency of 
respiration. 
The Hering-Brener stretch reflex is absent 
in the first weeks following lung replantation 
(Figure 5) . In general, it appears that there is 
early degenerative change in the vagus nerve 
fibers following replantation, as seen in serial 
sections taken at varying number of days (Fig- 
ure 6). However, re-examination of the lung 
with biopsies taken a number of months later 
shows stability of the nerve, with normal- 
appearing unmyelinated nerve fibers (Figure 
6). Thus, there is partial anatomic recovery 
of the vagus nerve, but the degree and fre- 
quency of return of anatomic and functional 
integrity of the vagus nerve months or years 
after replantation is still a controversial point. 
Marshall and Gunning reported the return of 
the Hering-Breuer stretch reflex in a dog al- 
most 4 years after replantation of the left lung. 
In one animal so studied it appeared that ciliary 
activity, as reflected in the upward progress of 
a small amount of India ink, was essentially 
normal. (It should be noted here that ciliary 
activity is not completely dependent upon the 
integrity of the nerve supply to the lung.) In 
contrast, in a second animal the rate of ciliary 
movement on the replanted left side was only 
about one-third of that on the normal right 
side. These workers found no evidence that the 
function of the lung had deteriorated as long as 
4 years after replantation. In sum, it is now 
accepted that the nerves to the lungs do regen- 
erate in most animals, in varying degrees. 
Innervation is not essential for adequate respi- 
ratory function to permit survival, but the pul- 
monary innervation does contribute to the over- 
all quality and efficiency of respiration. 
Differential Division of Hilar Tissue 
A study was undertaken to identify the effects 
of differential division of the bronchial arteries, 
R. Side Occluded 
L Side Occluded 
L Side Occluded R. Side Occluded 
Figure 5. — EiFects of nerve division. Note that occlu- 
sion of the main bronchus to the replanted left lung, 
producing lung distention, caused no change in respi- 
ratory rhythm. However, distention of the innervated 
(normal) right lung promptly produced apnea. 
