324 



MR. F. E. BEDDARD OX THE 



[^"oy. 17, 



perforated by regular oval foramina, which commence two and a 

 half inches from the larynx and continue to within half an inch 

 of the lung. These apertures vary somewhat in size, 8 mm. being 

 one extreme and 3 or 4 mm. the other. They may be really 

 divided into two series. Twenty-six or twenty-seven (and it 

 should be said that this series comprises the largest foramina) 

 lie at approximately equidistant intervals, corresponding either 

 exactly or very nearly exactly to the middle of a large mem- 

 branous sac, which is plainly to be regarded as a hernia-like 

 outpushing of the lining membrane of the trachea. This series 



Text-fie-. 38. 



A more detailed view of two air-sacs and dividing septum in Ojphio^ihagus, 



A, intercostal vein ; B, intercostal artery (both resting upon septum which divides 

 two adjacent air-sacs) ; C. carotid ; T, trachea, with two perforations ; 

 V.A., vertebral artery; V.V., vertebral vein. 



of sacs surrounds the organs of the neck and practically obliterates 

 the coelom. The sacs are of about the same dimensions, an inch 

 or so in antero-posteiior diameter. So closely are adjacent sacs 

 pressed together that the bounding walls anteriorly and posteriorly 

 run straight across the neck. The appearance thus produced, 

 when the parietes of the neck are cut through deeply enough to 

 include the ventral wall of the sacs, would lead naturally, on a 

 superficial view, to the inference that A\-e haJ here to do with it 



