THE EMBRYOLOGY OF THE BIRD's LUNG 37 



shows tln-ee sucli buds uiul of the seventh day (fi^- 71)) shows four. 

 Tliese figures are evidently not drawn wdth the camera since 

 altliough the niunber represented is correct, the buds are too 

 widely separated and cover too much territory of the centi-al 

 lung tube. The sketch of the condition on the eighth or ninth 

 day (fig. 80) shows both ento- and ectobronchi as well as the ex- 

 panded end of the mesobronchus. It should be said that Re- 

 mak's figures represent the essential features of the anatomy of the 

 embryonic lung. They are somewhat out of proportion and they 

 show the great difficulty of study by transmitted light without 

 the aid of some especial method of injection. 



Selenka's studies ('6(3) of the development of the air-sacs of the 

 chick added a number of points to the anatomy of the avian lung. 

 His figure of the 3| day stage shows the occluded bronchus (fig. 

 2) . In the fifth day stage he illustrates for the first time, the be- 

 ginning of the embryonic vestibulum (his fig. 3) . In his sketch 

 of the sixth da}" stage he represents the bud of the first ento- 

 bronchus, not quite in position, how^ever, in reference to the ex- 

 pansion of the lung tube, being in his figure posterior instead of 

 anterior to the expanded part. His sketch of the condition on 

 the seventh day (his fig. 5) shows seven or eight outgrowths 

 (buds of ento- and ectobronchi) of the central lung tube. 



His figure of the lungs and air-sacs of the eleven day embryo is 

 very interesting and, as already stated, has been extensively 

 copied in text-books. On the right lung is sketched (2') the sac 

 that w^e have designated the lateral moiety of the interclavicular 

 sac and w^hich he designates ''cellula infra laryngeus, on the left, 

 not yet united" — ''stetz sich spater in die cellula axillaris fort." 

 Although this figure needs attention, and some correction, it is 

 for the methods at his command a good figure. This figure also 

 show^s on the right lung the mesial moiety of the interclavicular 

 sac, but it is represented on the wrong side of the bronchus. As 

 shown in our figures 21 and 47 it arises on the mesial side and 

 extends across the bronchus ventrally to the lateral side. 



The sketches of Selenka and of Remak, made by talented ob- 

 servers show the limitations of observing the internal structures 

 of the lung by transmitted light without the help of injections. 



