THE EESPIEATORY SYSTEM. 



253 



There are certain peculiarities in the lungs of animals which 

 are adapted to an upright posture (Man and Anthropoids) : — 



pharynx 

 larynx 



right cardin. jiein 

 right branch.. 



I. — 

 put. art 

 II. 



trachea 



left bronchus 



I. 



mesoblast 



II. 

 pul. buds 



III. 



mesoblast 



oesoph. 



Fig. 206. — The condition of the Bight and Left Pulmonarj' Buds in a 5th week 

 embryo. (After His). 



(1) Ramification of the Bronchi. — In quadrupedal mammals 

 the bronchus does not divide by a process of equal dichotomy, as 

 in man, but passes backwards in the lung as a main stem, which 



trach, 



left branch. 



D J or apic. br. 

 right branch, 

 right pulm. art 



D3 

 D*. 



Pig. 207.— Scheme of the Bronchial Ramifications in Quadrupedal Mammals. J), the 

 Dorsal Ramifications ; Fthe Ventral Ramifications. 



grows gradually smaller by giving off four dorsal and four ventral 

 bronchial branches (Fig. 207). In man this arrangement can 

 scarcely be recognised. The ventral branches in him have become 

 larger than the main stems. 



