148 TETRAO TETRIX. 



late line behind the tongue, and terminating behind the aper- 

 ture in a curved papillate flap. The posterior portion of the 

 internal nares oblong, narro%y ; the anterior linear ; the edges 

 of both papillate. The tongue is short, eight-twelfths of an 

 inch in length, broad, triangular, flat above, acute, emarginate 

 and papillate behind. The aperture of the glottis with two 

 papillate transverse flaps behind. 



The fauces are of moderate width. The oesophagus, which 

 is twelve inches long, has for two inches a diameter of an inch 

 and a quarter, then contracts to nine-twelfths. About the 

 middle it is anteriorly and laterally expanded into a very large 

 subglobose sac or crop, of which the posterior walls are re- 

 flected upwards over the trachea and oesophagus, and doAvn- 

 wards over the anterior part of the thorax, so that the portion 

 of the oesophagus which forms part of the sac is only about a 

 fifth of its whole leno^th. On entering the thorax, the ceso- 

 phagus contracts to a diameter of eight-twelfths, and then 

 enlarges to form the proventriculus, which is of an ovato-oblong 

 form. Its internal diameter, however, is not greater than that 

 of the rest of the oesophagus, its bulk being produced by the 

 interposition between its walls of numerous oblong, sacculated 

 or branched glandules, placed obliquely, and opening on small 

 rounded papillce on the inner surface, with numerous small 

 mucous crA^pts in the intervals. Some of these glandules are 

 half an inch long. The whole inner surface of the oesophagus 

 is abundantly supplied with mucous crypts, and the upper and 

 lower orifices of the crop, especially the latter, have the walls 

 thickened and furnished with scattered glandules. 



The stomach is a very powerful gizzard of a roundish, sub- 

 lobate or subrhomboidal form, considerably compressed. Its 

 structure may be described as follows : On the middle of each 

 of its two flattened surfaces is a roundish thin tendinous centre, 

 from which on each side diverge tendinous filaments terminat- 

 ing in muscular fibres, which thus pass from the one to the 

 other tendon, forming two very thick muscles, the inner fibres 

 of which are complexly reticulated, although disposed in laminas 

 attached to the subjacent coat. Of these, the lateral muscles, 

 the left is somewhat larger, and has a thickness of nine-twelfths, 



