THE EMBRYOLOGY OF THE BIKD's LUNG 479 



Sappey, in 1847, described two principal kinds, the diaplirag- 

 niatics (bronches diaphragmatiques), branching towards the ven- 

 tral face, and the costals (bronches costales), extending dorsally 

 below the ribs. 



In 1875, in his extensive memoir, Campana designated three 

 categories: primary, secondary and tertiary bronchi. The pri- 

 mary (La bronche primaire, ou Souche) is the central lung tube 

 commonly called mesobronchus. He distinguished four groups 

 of secondary bronchi which we have adopted mth some modi- 

 fications. Campana's divisions are: (1) The system of five large 

 divergent bronchi (the diaphragmatiques of Sappey) ; (2) The 

 system of eight internal bronchi (the costales of Sappey) ; (3) 

 The system of six external bronchi, for which we have adopted 

 Schulze's term of laterobronchi (lateribronchi) ; (4) The system 

 of posterior or dorsal bronchi for which we employ the term dor- 

 sobronchi (dorsilateribronchi of Schulze). 



The tertiary bronchi, or terminal branches of subdivisions of 

 the secondary, are commonly known as parabronchi or air-pipes. 



Huxley, in 1882, introduced the terms mesobronchium for the 

 central lung tube, and en to- and ectobronchia for the diaphrag- 

 matics and the costals; w^e have adopted these simplified terms. 



While on anatomical grounds some critical objections may be 

 made to certain groups, we have, nevertheless, purely for descrip- 

 tive purposes adopted the following terminology: 



For the primary liuig tube, mesobronchus with its three divi- 

 sions, anterior, middle and posterior. 



Fig. 27 Air injected lung of an embryo of 5 days 9 hours incubation showing 

 the bud of the first entobronchus and the beginnings of the second. 



Fig. 2S Lateral aspect of the air injected lung of an embryo of 5 days 20 hours 

 incubation. 



Fig. 29 The same specimen rotated so as to be viewed from the dorso-lateral 

 aspect. This figure and the preceding show the establishment of the four entc- 

 bronchi in front of the dilatation of the mesobronchus. 



Fig. 30 Dorsal aspect of both lungs of a chick embryo of G days 6 hours incu- 

 bation. Shows the appearance of the bronchial tree when injected with air as 

 explained in the text. 



Fig. 31 Lateral view of the air injected lung of an embryo of (] (hiys 6 hours 

 incubation. This specimen was slightly younger than the one sketched in figure 

 .30. Shows the four entobronchi and the buds for the first four ectobronchi. 



