PATHOLOGY: W. S. HALSTED 
77 
weeks later signs of a second, smaller fistula developed at a distal point just 
below and in front of the ear. A second operation, proposed frequently, was 
not acceded to until last spring, six and one-half years after the first. At 
this operation, performed by Dr. Mont Reid in my presence, remarkably 
interesting observations were made. The tiny aberrant artery had become 
dilated almost to the size of a goose quill, and the internal carotid which at the 
first operation was strikingly small, was as large as normal, or larger (lantern 
slide). The explanation of the sequence of events is, I think, clear. There 
were originally two fistulae. The chief of these being eliminated at the first 
operation, the second, distal to the first, functioned more and more freely 
in the course of the six and one-half years. The internal carotid, small at 
the first operation because it was central to the main fistula, became dilated 
after the subordinate or distal fistula became active; and the anomalous artery, 
also central to the main fistula, became greatly dilated consequent upon the 
shifting of the fistula to a distal position. 
B. Enlargement of the heart in cases of arterio-venous fistula and persistent 
ductus arteriosus. — A particularly interesting result of our clinical and experi- 
mental studies of arterio-venous fistula is the discovery that enlargement of 
the heart probably occurs, after a time, as a rule in the major cases. For ten 
years or more we have noted the condition of the heart in our patients with 
arterio-venous fistula and have, I believe, quite invariably found the heart 
enlarged — strikingly so in several instances. Dr. Mont Reid, of our Surgical 
Staff, has in preparation a report upon his experimental and clinical work on 
arterio-venous fistula in which he will offer convincing proof of our view that 
the fistula in its consequences may profoundly affect the heart as well as the 
veins and arteries. The skiagraphs (exhibit) show the effects of a fistula 
made three and one-half years ago by Dr. Reid between the carotid artery and 
external jugular vein of a dog. The veins of the neck on both sides are dilated 
and the carotid artery is dilated central to the fistula. The heart after two 
years shows slight enlargement, and after three years, as you observe, it has 
become pronouncedly increased in size. If the assumption is correct that 
the heart dilates in consequence of arterio-venous fistula it is important that 
the fact should be brought to the attention not only of surgeons but also of 
pathologists and internists who evidently have overlooked it. 
Our experimental and clinical observations on arterio-venous fistula and 
partial occlusion of large arteries may ultimately aid in the explanation of the 
sequelae of certain congenital anomalies of the heart and aorta. May we not 
regard the persistent ductus arteriosis as an arterio-venous fistula, the pul- 
monary artery and the right heart representing the venous side of the fistula? 
The enlargement of the left heart we might assume to be analagous to the 
dilation of the artery proximal to a fistula; and in the dilation of the right heart 
and pulmonary artery we recall the dilation of the veins. My studies on the 
subject of the dilation of an artery which we find occurs distal to a constrict- 
ing metal band and distal to the compression exercised by a cervical rib have 
