William Snow Miller 391 
“as a rule no artery passes to the periphery of the lobule.” The signifi- 
cance of the exceptions I failed for some time to appreciate. 
If sections be made at right angles to the pleura of a dog’s lung, in 
which the blood-vessels have been injected as above indicated, here and 
there, it will be seen that a branch of the pulmonary artery extends 
beyond the plane at which the others break up into capillaries. When this 
branch reaches the pleura it bends upon itself, gives off radicles to the 
pleura, then passes towards the center of the lobule for a short distance 
where it breaks up into capillaries (Fig. 1, P. A.). 
Fig. 1. Section of the lung of a dog taken at right angles to the pleura. 
Camera lucida tracing showing the relation of the blood-vessels to the pleura. 
The parenchyma of the lungs is omitted from the drawing. P=pleura pul- 
monalis. P. A.—pulmonary artery, one branch of which can be seen arching 
under the pleura and sending a small radicle to the pleura. P. V.=pul- 
monary vein, one branch of which originates from the network into which 
the pleural radicle of the pulmonary artery breaks up. 50. 
In sections, taken parallel to the pleura and which include the pleura, 
it will be seen that only a small portion of the pulmonary artery ap- 
proaches the surface and that this is situated nearly equi-distant from the 
branches of the pulmonary vein (Fig. 2). 
From the branches of the pulmonary artery, which extend to the pleura, 
a system of capillaries is formed which, in turn, empties into the radicles 
of the pulmonary vein (Fig. 1). 
The pulmonary veins, on the other hand, as they approach the pleura 
branch repeatedly, and all of these branches run for some distance in, 
or just beneath, the pleura (Figs. 1, 2). 
