THE EPIDERMIS AND ITS DERIVATIVES. 32!) 



growths of the mucous layer (Kolliker, No. 298). The ends of these 

 ingrowths dilate to form the true glandular part of the organs, while 

 the stalks connecting the glandular portions with the surface form 

 the ducts. In the case of the sweat-glands the lumen of the duct 



o 



becomes first established. Its formation is inaugurated by the ap- 

 pearance of the cuticle, and appears first at the inner end of the 

 duct and thence extends outwards (Ranvier, No. 311). In the 

 sebaceous glands the first secretion is formed by a fatty modification 

 of the whole of the central cells of the gland. 



The muscular layer of the secreting part of the sweat-glands is 

 formed, according to Ranvier (No. 311), from a modification of the 

 deeper layer of the epidermic cells. 



The Mammary Glands arise in essentially the same manner as 

 the other glands of the skin 1 . The glands of each side are formed as 

 a solid bud of the mucous layer of the epidermis. From this bud 

 processes sprout out, each of which gives rise to one of the numerous 

 glands of which the whole organ is formed. Two very distinct types 

 in the relation of the ducts of the glands to the nipple are found 

 (Gegenbaur, No. 313). 



BIBLIOGRAPHY OF EPIDERMIS. 



General. 



(304) T.H.Huxley. " Tegumentary organs." Todd's Cyrlopa-dia of Aunt, and 

 Physiol. 



(305) P. Z. Unna. "Histol. u. Entwick. d. Oberliaut. " Archiv f. niiki: Annt. 

 Vol. xv. 1876. Vide also Kolliker (No. 298). 



Scales of the Pisces. 



(306) O. Hertwig. "Ueber Bau u. Entwicklung d. Placoidschuppen u. d. Zahne 

 d. Selachier." Jennisehe Zeitschrift, Vol. vin. 1874. 



(307) 0. Hertwig. "Ueber d. Hautskelet d. Fische." Morphol. Jahrbuch, Vol. 

 n. 1876. (Siluroiden u. Acipenserida?.) 



(308) O. Hertwig. "Ueber d. Hautskelet d. Fische (Lepidosteus u. Polypterus)." 

 Morph. Jahrbuch, Vol. v. 1879. 



Feathers. 



(309) Th. Studer. Die Entwick. d. Federn. Juaug. Diss. Bern, 1873. 



(}io) Th. Studer. "Beitrage z. Entwick. d. Feder." Zeit. f. wiss. Zool., Vol. 

 xxx. 1878. 



Sweat-glands. 



(311) M. S. Eanvier. " Sur la structure des glandes sudoripares." Comptm 

 Rendus, Dec. 29, 1879. 



Mammary glands. 



(312) C. Creighton. "On the devel. of the Mamma and the Mammary function." 

 Jour, of Anat. and Pliys., Vol. xi. 1877. 



(313) C. Gegenbaur. "Bemerkungen iib. d. Milchdriisen-Papilleu d. Sauge- 

 thiere. " Jenaiache Zeit., Vol. vn. 1873. 



(314) M. Huss. "Beitr. z. Entwick. d. Milchdriisen b. Menschen u. b. Wieder- 

 kauern." Jenaische Zeit., Vol. vn. 1873. 



(315) C. Langer. "Ueber d. Bau u. d. Entwicklung d. Milchdriisen." Denk. d. 

 k. Aktid. Wiss. Wien, Vol. in. 1851. 



1 For a very different view on this subject riiJi- Creighton (No. 31 2). 



