390 The Vascular Supply of the Pleura Pulmonalis 
METHOD OF STUDY. 
in my study of the blood-vessels, I have used as a means of differenti- 
ating the various systems of vessels a 20 per cent solution of gelatine 
containing colored granules. If a Prussian blue or carmine gelatin be 
used, one can not be sure that a given network belongs to any individual 
system of vessels. If, on the other hand, the injection mass be charged 
with granules of such size that they will not readily pass the capillaries, 
then all the derivatives of the vascular trunk injected will stand out 
sharply and distinctly. I can not but think that this method of injection 
gives more exact results than the former. Take for example a lobe of a 
dog’s lung. A cannula is tied in the branch of the pulmonary artery 
which supplies the lobe; a second cannula is tied in the branch of the 
pulmonary vein coming from the lobe. A 10 per cent solution of Prussian 
blue gelatin is first injected into the artery until the lobe is thoroughly 
blue and the mass runs freely from the open cannula tied in the vein. 
The injection is now discontinued and a flask of 20 per cent gelatin 
containing vermilion granules is connected with the pulmonary artery 
and a second flask of 20 per cent gelatin containing Ultra-marine blue 
granules is connected with the pulmonary vein. These two granular 
masses are injected simultaneously. The result is that the capillaries are 
filled with a transparent blue mass; while the pulmonary artery and its 
branches are opaquely red; the pulmonary vein and its branches are 
opaquely blue. There is no mistaking one set of vessels for the other. 
It is by means of various modifications of this method that the present 
study has been made. 
Dog.—In the dog, repeated injections of a granular mass, prepared as 
above, directly into the bronchial artery have failed to demonstrate any 
branches passing to the pleura. Only at the hilus have I seen short twigs, 
two to five millimeters in length, given off from the main stems of the 
bronchial artery, these were distributed to the connective tissue about 
the hilus of the lung and did not extend to the pleura. I have also failed 
to find any branches of the bronchial artery extending from the depth of 
the lung to the pleura. It seems quite probable that the absence of 
pronounced connective-tissue septa in the dog’s lung is an important fac- 
tor in the arrangement of the bronchial artery. 
Kiittner (8) has described branches of the bronchial artery as being 
distributed directly to the pleura and anastomosing with the pulmonary 
artery. My injections have failed to confirm his results. 
I have previously stated in regard to the pulmonary artery (9), that, 
