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ation, the lateral surfaces of the primitive lung sacs show stages pre- 

 paratory to the formation of the second lateral bronchi which are 

 paired and originate as lateral evaginations from the walls of the two 

 sacs. At 9 mm they may be plainly seen als lateral outgrowths from 

 the sides of the stem bronchi, while the terminal buds have already 

 grown somewhat farther caudalwards. In a pig 10 mm in length, 

 the unpaired Lateral 1 on the trachea and the paired second lateral 

 bronchi on the stems have developed to approximately the same extent, 

 but on the wall of the right stem bronchus above the end bud, two 

 slight outgrowths or evaginations appear indicating the origin of 

 Ventral 2 (the Bronchus infracardiacus), on the ventral side, and 

 Dorsal 2 on the dorsal side of the stem. Neither of these buds is 

 connected with the lateral bronchus just above them ; the third laterals 

 below are as yet unformed. These dorsal and ventral bronchi, like 

 the lateral branches above, are productions of monopodial growth. In 

 the next stage, shown by pigs 12 mm long the simple tree is still 

 asymmetrical, and Lateral 1, and Lateral 2 on each side are in a 

 stage preparatory for division; Ventral 2 on the right side has in- 

 creased considerably in size while Dorsal 2 remains as a slight pro- 

 jection. A Dorsal 2 has appeared in a similar way on the stem of 

 the left bronchus, but a branch corresponding to Ventral 2 is never 

 formed in the pig. Lateral 3 is already present on each side and 

 the stem continues caudalwards to end in a bud preparatory for the 

 formation of the next pair of lateral branches. These elements like 

 the remainder of the lateral series are produced by monopodial out- 

 growths of the sides of the end buds. 



The next stage, 13,5 mm, shows the division of Lateral 1 and 

 Lateral 2 on each side by dichotomy, while the rest of the lateral 

 series on the right side is formed as far down als Lateral 5 which is 

 shown as a simple swelling on the side of the end bud. On the left 

 side only Laterals 2, 3, and 4 are formed. Ventral 2, the infracardiac 

 bronchus, although undivided is now almost as long as Lateral 2, while 

 Ventral 3, on the right side, is shown as a slight projection from the 

 stem bronchus, midway between Laterals 3 and 4, 



On the left side only one of the ventral series is present, namely, 

 Ventral 3, which is situated on the stem between Laterals 3 and 4. 

 The dorsal series in this specimen shows great variation ; Dorsal 2 on 

 the right side lies midway between Laterals 2 and 3 ; Dorsal 3, however, 

 is just under Lateral 3, while Dorsal 4 is suppressed. On the left 

 side, Dorsal 2 is just above Lateral 3, while Dorsal 3 is almost at 

 the level of Lateral 4. In this lung, the medial series of bronchi is 



Anat. Anz. XXVlll. Aufsätze. IS 



