THE SYRINX OF GALLUS DOMESTICUS 199 



mammals the stratified ciliated columnar epithelium of the larynx 

 is transformed into the stratified squamous layer over the true 

 vocal cords, and submucous glands are absent, so in case of the 

 sjrrinx of the chicken the stratified ciliated columnar epithelium 

 is changed into a squamous epithelium over the tjnnpanic mem- 

 branes. This squamous epithelium, however, is composed of but 

 a single layer. The prominent glands of the mucosa are also 

 absent from these membranes. 



The semilunar membrane was belie^^ed by Savart, Wunder- 

 hch, and others, to play an important part as a vibrating struc- 

 ture. It is said to be more prominent in songsters than in other 

 birds, but Hacker ('00) pointed out that in black birds its epithel- 

 ium is of the stratified cihated columnar type, and that it proba- 

 bly is not of much importance in the production of voice, and 

 also that it is often as well developed in songless species as in the 

 best songsters. This structure certainly does not act as a vi- 

 brating membrane in the chicken for it is covered with stratified 

 ciliated columnar epithelium, and mucous glands are just as 

 abundant in it as in any unmodified part of the epithelium. 



CONCLUSIONS 

 STRUCTUEE 



1. The syi'inx of the domestic chicken belongs to the tracheo- 

 bronchialis type, and is quite simple when compared with the 

 voice organ of song birds. 



2. No intrinsic muscles are present in the syrinx of Gallus 

 domesticus. The extrinsic paired sternotrachealis with its cau- 

 dal prolongations constitute the entire musculature of the syrinx. 



3. The rigid skeleton is very highly modified. The first four 

 tracheal rings are imperfectly fused to form the tympanum. The 

 four intermediate syringeal cartilages are continuous ventrally 

 with theii ventral pyramid of the pessulus, while dorsaUy they 

 end unattached. The first bronchial half-rings are large and in 

 adults are attached and fused at both ends to the pessulus. The 

 pessulus is the largest of all skeletal parts and lies dorso- ventrally 

 at the junction of the bronchi, in a plane transverse to the long 



