2 PROCEEDINGS OF THE NATIONAL MUSEUM vou 67 



indebted. J. Eugene Law, Altadena, Calif., provided me with 

 much valuable fresh material, as did also George Willett, Los An- 

 geles, Calif., to both of whom I wish to express my thanks. 



Finally I am much indebted to Prof. Charles F. Baker, Los Banos, 

 Philippine Islands, for his assistance, and to my wife for her aid in 

 the preparation of the illustrations. 



Before reviewing the variations undergone by the tongue a brief 

 consideration of the histology may be of interest to throw some light 

 on the function. 



ANAS PLATYRHYNCHOS 



A cross section through the anterior one -third of the tongue re- 

 veals the following: The section is very irregular in shape, with a 

 deep groove dorsally. In the center of the tongue is the single car- 

 tilaginous and bony mass of the fused ceratohyals. Surrounding 

 this is a complex interlacing of adipose and connective tissue, strati- 

 fied skeletal muscle, blood vessels, and nerve trunks. Embedded 

 deeply in tissue are found groups of mucous glands, ducts of which 

 here and there can be traced to the dorsal surface of the tongue. 

 Dorsolaterally is seen a double row of cornified spines or hairs, 

 from the base of which strands of cells are scattered deeper into the 

 tongue. Small nerve corpuscles are seen grouped chiefly about the 

 cornified spines. Finally the surface of the tongue is composed of 

 stratified epithelium through which ducts of mucous glands pass. 



TYTO PRATINCOLA 



The extreme tip of the tongue is composed almost entirely of corni- 

 fied epithelium. Posterior to this on section the tongue is concave 

 dorsally, the epithelium covering this surface being a relatively thin 

 layer. The center of the tongue is occupied by the bony mass of the 

 ceratohyals surrounded by connective tissue with interlacing fibers 

 of striated muscle. At the mid point between the tip and posterior 

 margin of the tongue mucous glands make their appearance, and 

 from this point posteriorly become abundant. 



The glands in this species are quite superficial, being embedded 

 in the layer of stratified epithelium itself and opening to the sur- 

 face through pores which are visible, with the unaided eye or a 

 small lens, on gross inspection. Nerve corpuscles are either absent 

 in this species or very infrequent. 



PICA NUTTALLI 



On section the tongue is concavo-convex, with the concavity rep- 

 resenting the dorsal surface. The ventral surface is composed of 

 cornified epithelium. The dorsal surface is covered with a deep 

 layer of noncornified stratified epithelium. Glands in this species 

 do not appear except at the extreme posterior portion of the tongue. 

 Nerve corpuscles are infrequent. 



