166 GEO. S. HUNTINGTON 
medial stretch there are four of these points, viz., the ventral, 
ventro-medial, medial and dorso-medial. 
One or more of these secondary points may give origin to 
secondary or accessory bronchi or they may default. 
In the first case, depending upon the number and location of 
the points utilized, the stembronchus will be studded more or less 
profusely in the intervals between the lines of its principal 
ventro-lateral and dorsal bronchi with smaller secondary accessory 
bronchi. In the second case these portions of the stembronchus 
are naked. Conditions in this respect vary at different horizontal 
levels. In general accessory bronchi become more numerous in 
proceeding cranio-caudad along the stembronchus. This ac- 
cords with the more archeal type of bronchial distribution in the 
caudal reaches of the lungstem. They preponderate numerically 
in the medial as compared with the lateral sector of the circum- 
ference of the stembronchus, the former presenting a greater 
are, and hence more points for their development than the latter, 
in the proportion of 4:2. The development of lateral and dorso- 
lateral accessory bronchi is further restricted by the course of 
the main pulmonary artery which for the greater part of its 
extent lies typically against the dorso-lateral surface of the stem- 
bronchus, between the rows of the main ventro-lateral and the 
dorsal primary bronchi. The budding of the epithelium lead- 
ing to the development of the accessory bronchi is not limited to 
the mathematical point of the compass indicated by their desig- 
nation. Thus a member of the dorso-medial group may develop 
anywhere between the lines D and M, a ventro-medial accessory 
bronchus anywhere between M and V, etc. If it occupies the 
latter point it may form either one of the rarer accessory bronchi 
passing directly ventrad, or a ventrally located bud more com- 
monly swings mesad in attaining its distribution and supplies a 
typical ventro-medial pulmonary district. Still further the main 
primary dorsal and ventral bronchi represent, as above stated, 
the stembronchi for the secondary lung-sacs, forming their axial 
conducting structure. Like their prototype, the main stem- 
bronchus, they retain the same potency for proliferation from 
any point of their circumference. Thus a given ventro-medial 
