300 A. 0. V. T;/mw.f<: 



The mesob roil elms of the lung, while passing from the medial to 

 the lateral region of the lung, gives off its third entobronchus. (Pis. 

 XXIII. and XXIV., figs. 17, 18, 22.) The third entobronchus is 

 directed medially and ventrallv. and subdivides into three main 

 branches. Almost immediately it gives off its first bramh, which is 

 directed caudally, medially, and slightly dorsally. and is confined 

 to the lung itself. (PI. XXIV., figs. 18, 22.) The stem then passes 

 ventrally, and in the ventro-medial region of the lung, bifurcates, 

 the slightly smaller branch is the stem of the interclavicular sac, or 

 syringeal air sacs, and is directed cranially and ventrally tow^irds 

 the interbronchial region. (PI. XXL, fig. 11.) Tht* other sub- 

 division passes ventrally, and expands into the laige anterior thor- 

 acic air sac. (Pis. XXIII. and XXIV., figs. 17-24.) Tlie stem of the 

 syringeal air sacs, after emerging from the lung, passes up close tu 

 the ventro-medial region of the bronchus, and begins to expand into 

 several large air sacs, Avhich take up different positions, in relation 

 to different parts of the syrinx. (Pis. XXL, XXIII. and XXIV., figs. 

 11, 17, 19.) There are three main sacs arising — a ventio-lateral 

 interbronchial, and dorsal, Avhich latter is the continuation of the 

 stem. 



The ventro-lateral one passes over the bronchus and ventral 

 triangular plate, and takes up a position in relation to tlie whole 

 ventro-lateral region of the syrinx and lu-onchus. (Pis. XXI. and 

 XXII. , figs. 11-U.) 



On the right side the interbronchial sac passes up between tlie 

 bronchi as far as the pessulus, and extends to the left bioncluis, stv 

 as to iovm the inner boundary of both membranae internae. 

 , On the left side the sac is much smaller, not reaching to tlie 

 pessulus, and confined to its own side. (Pis. XXI. and XXII., figs. 

 11-13.) 



The third main sac, or dorsal one, is large, and gives off three 

 main divisions before terminating. (Pis. XXL, XXIL, XXllL. 

 tigs. 11-16.) The most cranial one passes laterally beliimt 

 the bronchus into a lai-ge expanded sac occupying the whole 

 of the dorso-lateral re{j:ion of the syrinx. Just caudally. tlie 

 second smaller division also passes dorso-laterally, beneatii the 

 bronchus, to the lateral side. The third division is large, and ])asses 

 laterally, giving off divcrtieula to the upjter vt'Liion of the hiiig. 

 It passes dorsal to, the bronchus, and in close lelation to the inno- 

 minate artery. This is the recurrent bronchial branch of the in- 

 terclavieular sac. (PI. XXIII. . fig. 15.) After giving off its three 

 main divisions, the main dorsal sac terminates in several small 



