68 



On the Lung of the Opossum 



tion, found on p. 159 of his '^ Entwickel ungsgeschichte der Tiere," is 

 as follows : 



" The lungs of opossum have to develop into functioning breathing 

 organs within the last three days of uterine life. There is neither the 

 available material nor the necessary time to make a very great number 

 of alveoli and prepare them for breathing (as is completely done in 



Fig. 2. Opossum, 13.5 mm. frontal. Series 618, No. 838. Pul. art, pulmonary 

 artery ; pul. ve, pulmonary vein ; oes, oesophagus ; pr, new bronchial bud ; card, 

 part of cardiac lobe. 



foetal life in placentalia) . Only a few dozen large air-chambers, as a 

 provisional breathing apparatus, can be made, which later, during the 

 life iji the pouch, develop by the growth of partitions into a richly 

 branched bronchial tree. The lung may be said to be of rapid growth 

 inasmuch as the alveoli are ready for breathing in a remarkably short 

 time; but its growth is slow if we consider the increase in the number 



