William Snow Miller 405 
taining vermilion granules should pass freely from one set of vessels to 
the other set of vessels, as is illustrated in the anastomoses between the 
superficial and deep bronchial arteries in the lung of the sheep where the 
anastomosing branches are discernible to the eye (Fig. 6). 
In the present study, and also in my study of the bronchial artery 
within the lung, I have failed to demonstrate by the use of granular 
injecting masses any anastomoses between the bronchial and pulmonary 
arteries. On the other hand, by using injection masses which flow freely 
through the capillaries I have injected both sets of vessels but only by a 
backward flow of the injecting mass through the capillary network (9 e). 
In my study of the bronchial artery of the pleura of the lung of man, 
in one instance, I inserted a cannula directly into a branch of the 
bronchial artery and injected an aqueous solution of Berlin blue. On 
cutting into the lung it was seen that the fiuid had ‘entered both the 
pulmonary vein and pulmonary artery. Serial sections showed that the 
fluid had followed the capillaries, the pulmonary artery being injected 
indirectly. This can in no way be interpreted as showing an anastomosis 
between the two arterial systems, for it is absurd to call an indirect 
capillary communication an anastomosis. 
VASA VASORUM OF THE PLEURAL LYMPHATICS. 
The presence of a network of blood-vessels about the lymphatics has 
been overlooked by most of the later investigators but was recognized by 
those of the eighteenth and early part of the nineteenth centuries. 
Cruikshank, for example, says: “I have injected, in quadrupeds, the 
arteries on the coats of the lymphatic vessels, and seen them ramifying 
very elegantly through their substance (1).” 
Panizza (11), searching for the origin of the lymphatics, says that 
whenever he has seen the injection appear in the lymphatics, after having 
completely filled the blood-vessels, he has found a network of capillary 
blood-vessels of a microscopical tenuity surrounding the lymph vessels. 
He concludes from this that the passage of the injection is a phenomenon 
of porosity. Evidently, Panizza overlooked the possibilities which might 
result from a rupture of this network of capillaries. 
Sappey (13) and Dogiel (2) seem to be the only modern investigators 
who have recognized the vasa vasorum of lymph vessels. Sappey says: 
“The lymphatics are provided with vasa vasorum which one can very 
easily observe under the microscope and follow into the thickness of their 
walls.” In another place he says the wall of the lymphatic trunks is rich 
in vessels and nerves. Hach pulmonary lymphatic, for example, being 
encircled by a blood vascular network with coarse longitudinal meshes. 
