435 



network is carried away from these divisions by two small veins 

 which arise one on either side of the bronchiolus respiratorius and 

 by analogous veins which arise from the distal end of the ductulus 

 alveolaris. These latter are the only veins found within the lobule. 

 In a previous publication I have described and figured these two sets 

 of veins i). 



By a careful study of the vascular network in the bronchial 

 mucosa one can recognize small areas composed of an arterial radicle, 

 its capillaries, and a loop of the venous plexus. I have found this 

 area in the bronchi of man, of the dog, and of the cat. It may be 

 called the unit of distribution (Fig. 1 * and Fig. 2). 



Fig. 



Fig. 3. 



Fig. 2. The unit of distribution indicated by the * in Fig. 1. The arterial 

 radicles are shown in solid black; the venous radicles and capillaries in outline. 

 Fig. 3. A variation of the unit shown in Fig. 2 occasionally met with. 



No anastomoses were found between the bronchial and pulmonary 

 arteries. Relatively large branches of the bronchial artery could, in 

 several instances, be traced to the walls of the pulmonary artery where 

 they formed the vasavasorum, but in no instance was the differential 

 injection mass found in the lumen of the pulmonary artery. It seems 

 quite probable that rupture of these vessels into the pulmonary artery 

 has in previous investigations given rise to apparent anastomoses 

 between the two sets of vessels. 



In studying the question of anastomoses five sets of injections 

 were made, using the lungs of dogs weighing from 20 to 21 kilos. 



1) W. S. Miller, Das Lungenläppchen, seine Blut- und Lymph- 

 gefäße. Arch. f. Anat. u. Physiol., Anat. Abt., 1900, Taf. 11, Taf. 12, 

 Fig. 4 and Textfigure f. 



28* 



