Ixxi 



cies, that is, two barbs proceeding from one quill ; the barrel 

 of the latter Is small, and filled with pith, and the feathers are 

 fine and hair-like. This, indeed, is the general character of 

 the plumage of the struthiones. 



A few days after the death of one of these birds (a female), I 

 carefully examined the sac, larynx, and trachea, and the follow- 

 ing is an accurate account of the several appearances. The 

 integuments covering the air-bag differ in no respect from the 

 general investment of the neck ; beneath the skin is a strong 

 and red muscular lamina, expanded over its sides and fore- 

 part; the fibres are chiefly longitudinal, but several strong- 

 fasciculi run in different directions; the subjacent areolar 

 tissue contains numerous nerves and vessels, especially veins. 

 On opening the bag, the tracheal orifice (fig. 2) is seen dis- 

 tinct and well-defined, of the form of a long parallelogram ; 

 the mucous membrane of the tube is continued around its free 

 margin, is reflected over, and adheres to the anterior and 

 lateral parts of the tube considerably beyond the edges 

 of the opening, and then expands in all directions to line 

 this capacious reservoir, which is suflBciently large to con- 

 tain at least a quart or three pints of fluid. This mem- 

 brane is soft and vascular; numerous capillaries and large 

 veins, with long tortuous nerves, are seen distinctly through 

 it. The tracheal opening (fig. 4) is situated about three 

 inches above the furculum, and in the middle line of the 

 tube ; it is two inches and a half long, and scarcely half an 

 inch wide, but it can be easily extended to three inches 

 in the vertical and to three-quarters of an inch in the transverse 

 direction; it is produced by a deficiency in the anterior part 

 of six rings (in the two specimens 1 have examined the num- 

 ber was the same) ; the cartilage above and that below the 

 opening is broad and well defined ; the extremities of the six 

 lateral cartilages are sharp, thin, and very moveable ; there is 

 no dilatation, at least to any appreciable degree, in this part of 

 the tube, and the rings are not all extended or continued into 



