THE PHARYNX. 499 



in Zeitschr. fur. wiss. Zool." 1850, bd. II. p. 295; Arnold, in " der 

 Salzblirger med. Zeitung," 1831, p. 236 ; Raschkow, " Meletematacirca 

 dentiura mammalium evolutionem," Vratisl. 1835; Goodsir, in " Edinb. 

 Med. and Surg. Journal," 1838, No. XXXI. 1; and Froriep's " Neue 

 Notizen," Nos. 199, 200, 202, 203; Marcusen, " Ueber die Entwick- 

 lung der Zahne der Siiugethiere," aus dera " Bulletin Phys. Math." VIIL, 

 No 20, Petersburgh, 1850. On Dental Caries consult Erdl. in " Allg. 

 Zeitung flir Chirurgie von Rohatzsch," 1843, No. 19 ; Ficinus, in 

 "Journal fur Chirurgie von Walther and Ammon," 1846, p. 1 ; Klenke, 

 "Die Verderbniss der Ziihne," Leipsig, 1850. The Comparative 

 Anatomy of the teeth is treated of microscopically in the works of Owen 

 and Retzius above cited ; also by Erdl, in the " Abhandlungen der 

 Math. Phys. Klasse, der Konigl. Bayer. Akad." bd. III. Abth. 2 ; 

 Tomes, in the "Phil. Trans." 1849-50 (Marsupialia and Rodentia) ; 

 Agassiz, in the "Poissons fossiles ;" Henle and J. Muller, " Syst. 

 Beschreibung der Plagiostomen," 1838. 



[To these should be added: Blake, "Essay," c., 1801; Hunter, 

 "Treatise on the Natural History and Diseases of the Human Teeth," 

 edited by Thomas Bell (Works by Palmer, 1835, vol. ii.) ; Tomes, "On 

 the Structure of the Teeth, the Vascularity of those Organs, and their 

 relation to Bone," Proceedings of the Royal Society, June, 1838 ; Owen, 

 " On the Structure of the Teeth, and the resemblance of Ivory to Bone," 

 British Association Reports, 1838; Nasmyth, " Medico-Chirurgical 

 Transactions," 1839 ; "Proceedings of the British Association," 1839; 

 " Researches on the Development, Structure, and Diseases of the Teeth," 

 1849 ; Huxley, " On the Development of the Teeth," " Quarterly 

 Journal of Micr. Science," 1853; Salter, "On certain appearances 

 occurring in Dentine," ibid. 1853. TRS.] 



OF THE ORGANS OF DEGLUTITION. 

 I. THE PHARYNX. 



144. The alimentary canal assumes a greater independence in the 

 pharynx, acquiring a special investment of transversely striated muscles, 

 the constrictores and levatores, which, however, do not entirely surround 

 it and arise for the most part from bones. The thickness of the walls 

 of the pharynx is about 2 lines on an average, depending principally 

 upon this muscular layer, external to which there is a tense fibrous mem- 

 brane, composed of connective tissue and elastic fibres, while internally 

 it is separated by a layer of submucous connective tissue from the 

 mucous membrane. The latter is paler than that of the oral cavity and 

 its structure in the upper half of the pharynx differs considerably from 

 that in the lower half. In the latter locality, that is, below the pha- 

 ryngo-palatine arches, or in the region through which the food passes, 

 it possesses a tessellated epithelium similar in structure and thickness to 



