THORACIC CAVITY 59 



which lie in the substance of the lungs are the intra-pulmonary 

 parts, and an attempt should now be made to display their 

 main relations. 



Dissection. Place the lung with its mediastinal surface 

 uppermost ; then follow the pulmonary veins into its substance. 

 They lie in front of the main parts of the bronchi. On the right 

 side commence with the upper pulmonary vein. At the hilum 

 it will be found to receive two tributaries, one emerging from 

 the upper lobe, and accompanying the eparterial bronchus, and 

 the other issuing from the middle lobe, accompanying what will 

 afterwards be found to be the first ventral hyparterial branch 

 of the bronchus. It also receives a tributary from the medial part 

 of the lower lobe. As the vein and its tributaries are cleaned, 

 clean also the anterior aspects of the bronchi. Next, follow the 

 inferior pulmonary vein ; it accompanies the stem bronchus, 

 below the level of its first ventral hyparterial branch, and it re- 

 ceives tributaries which correspond to all the hyparterial branches 

 of the bronchus, except the first ventral branch and a small branch 

 called the first ventral accessory bronchus which is given off 

 from the front of the stem bronchus immediately below the first 

 ventral hyparterial branch. After the veins have been cleaned 

 follow the eparterial bronchus for a short distance into the 

 substance of the upper lobe and note that it is the only bronchus 

 distributed to that lobe. Next clean the hyparterial bronchus 

 and attempt to display its two main sets of branches, ventral and 

 dorsal. They will be recognised in the adult by their black 

 or greyish-black colour. As the bronchi are being cleaned 

 small pulmonary lymph glands will be met with in the angles 

 between their branches. The ventral branches spring from 

 the lateral border of the stem bronchus and run towards the 

 anterior margin of the lung. The first ventral branch is the only 

 branch distributed to the middle lobe (Fig. 25). The remaining 

 three or four ventral branches and all the dorsal branches pass 

 to the lower lobe. 



The dorsal branches arise from the back of the hyparterial 

 part of the stem bronchus and pass towards the thick posterior 

 border of the lung. Clean them from their medial sides. Note 

 that the ventral and dorsal branches arise alternately first a 

 ventral, then a dorsal. As the dissection proceeds the dissector 

 will find some small hyparterial branches which lie intermediate 

 between the ventral and dorsal branches ; they are called acces- 

 sory bronchi. Only one of the group of accessory bronchi is of 

 special interest. It springs from the front of the stem bronchus 

 immediately below the first ventral branch ; it is, therefore, the 

 second branch from the hyparterial part of the stem bronchus, 

 and is the first ventral accessory bronchus (Fig. 25). It is of 

 special interest because it is distributed to a portion of lung 

 substance which occasionally becomes a separate lobe called 

 the infracardiac lobe, the right lung then possessing four lobes. 

 The artery which accompanies the first ventral accessory bronchus 

 is frequently a branch of the artery to the middle lobe, and the 

 vein terminates in the vein from the middle lobe. 



After the bronchi have been cleaned follow the intra-pul- 

 monary part of the pulmonary artery, as it descends along the 



