. The American journal of anatomy . ical right artiodactyl lung far ex-ceeds the corresponding element of the opposite organ, extendingacross the median line and actually in many species fitting overthe apex of the left lung. The peripheral respiratory area re-sulting from the unfolding of a terminal bronchiole is practicallya constant value in each mammalian form. Increase in the 154 GEO. S. HUNTINGTON respiratory surface spells a corresponding increase in the numberof the terminal bronchioles. It is a simple mathematical propo-sition to prove that the number of the ultimate bronchioles andth
. The American journal of anatomy . ical right artiodactyl lung far ex-ceeds the corresponding element of the opposite organ, extendingacross the median line and actually in many species fitting overthe apex of the left lung. The peripheral respiratory area re-sulting from the unfolding of a terminal bronchiole is practicallya constant value in each mammalian form. Increase in the 154 GEO. S. HUNTINGTON respiratory surface spells a corresponding increase in the numberof the terminal bronchioles. It is a simple mathematical propo-sition to prove that the number of the ultimate bronchioles andthe consequent area of the respiratory surface will depend, withthe same type and ratio of division of the bronchial tree, upontheir caliber and upon the distances separating the origins ofthe primary conducting tubes from the stembrbnchus. Thus in the case of the right eparterial bronchus (A) the extentof its respiratory area is in direct ratio to the distance X-Y sep-arating it from the next adjacent derivative (B) of the stembron-. Fig. 6 Schema of bronchial and tracheal derivation of right eparterialbronchus. A., eparterial bronchus; B., first ventral hyparterial bronchus. chus, the first ventral hyparterial branch. In comparing thedominant type (fig. 6^) with that obtaining in the artiodactyls(fig. 6^), the enlarged respiratory capacity of the latter is meas-ured by the greater length of the line X-Y. The phyletic as well as the ontogenetic interpretation of themigratory theory would hold that the tracheal eparterial bron-chus in the ancestors of the modern artiodactyls was a branch ofthe first ventral bronchus, which in the course of evolution emi-grated from this primitive site craniad, first onto the stembron-chus, and then still further in the same direction beyond the bifur-cation a variable distance up along the right side of the trachea. PULMONARY EVOLUTION IN MAMMALIA 155 In all these wanderings the bronchus retained its own individualcharacter, always representing t
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectanatomy, bookyear1920
