176 JAY ARTHUR MYERS 



to account for all the differences observed. Quite naturally the 

 sterno-tracheal muscles are noticeably smaller in females; but 

 the bony rings above the tympanum, these, in the male (fig. 5) 

 are entirely different in size and shape from the corresponding 

 rings in the female (fig. 6) . Again, in the male the tympanum 

 is composed of the first four tracheal rings, while in the female 

 only the first three form this structure. The tympanic mem- 

 branes, however, exhibit no marked difference. 



It is not an uncommon thing to hear a female chicken try to 

 crow. The sounds she produces are distinct, and cannot be 

 mistaken for anything other than an attempted crow. Judg- 

 ing from the structure of the syrinx, there is no apparent reason 

 why the female should not be able to crow perfectly, provided 

 the instinct for it were properly developed. Hacker ('00) calls 

 attention to the fact that the females of certain species of song 

 birds, when kept in captivity, learn to sing as charmingly as the 

 males. Barrington (1773) gives numerous examples of one 

 species being trained to sing the song of another species. 



2. Microscopic anatomy 



For this phase of the investigation, cross, coronal, and longi- 

 tudinal sections were made through the sj^inx of both male and 

 female adult chickens. The sections were cut five, ten, fifteen, 

 and twenty micra in thickness. The following stains were used : 

 iron hematoxyhn, picrofuchsin, Malloru's aniline-blue connec- 

 tive tissue stam, Weigert's resorcm-fuchsin elastic tissue stain, 

 Unna's orcein, and Mayer's mucicarmine. 



In figure 5 all of the rings, the half-rings, the cartilages, and 

 the pessulus are seen in cross section. It is to be noted that the 

 tracheal rings cephalad to the second are completely ossified. 

 Each consists of a thick peripheral layer of compact bone mthin 

 which is a central area of cancellous bone. A distinct periosteum 

 surrounds the whole. The cavities of the cancellous portions 

 contain bone-marrow not unlike that found in other bones of 

 birds. 



As stated before, the first fom- tracheal rings are united to 

 form the tympanum. The first two rings are composed of hya- 



