. Elements of comparative anatomy. Anatomy, Comparative. Fig. 218. Vertical section through the skin of an Embryonic Shark. C Corium. c, c, c Layers of the corium. d Uppermost layer, p Papilla. E Epidermis, e Its layer of columnar cells, o Enamel layer. formations, to which indeed they completely correspond in the higher divisions. The dermal denticles (placoid scales), which are distri- buted over the whole of the in- tegument in the Selachii, may be regarded as the structures from which the various forms have been derived. In them we distin- guish a basis, which is inserted into the corium,
. Elements of comparative anatomy. Anatomy, Comparative. Fig. 218. Vertical section through the skin of an Embryonic Shark. C Corium. c, c, c Layers of the corium. d Uppermost layer, p Papilla. E Epidermis, e Its layer of columnar cells, o Enamel layer. formations, to which indeed they completely correspond in the higher divisions. The dermal denticles (placoid scales), which are distri- buted over the whole of the in- tegument in the Selachii, may be regarded as the structures from which the various forms have been derived. In them we distin- guish a basis, which is inserted into the corium, and is ordinarily rhom- boidal in shape, and a portion, which stands out from it, and which ordinarily has its apex directed obliquely. This is covered over by the epidermis. In some parts, as, for example, on the head, they often have a bombous surface, and are set irregularly; while on the trunk they are generally set in per- fectly regular and obliquely running rows (). They are developed on papillas of the corium (, p), which are covered over by a layer developed from the epider- mis : this secretes an enamel-like substance on the projecting por- tion of the papilla, while the body of the papilla is ossified from the tip downwards. The epidermis and corium, therefore, both share in the formation of these structures. There is a central cavity in the. Fig. 219. Dermal denticles of Centrophorus calceus (a little magnified).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gegenbaur, C. (Carl), 1826-1903; Bell, F. J. (Francis Jeffrey), 1855-1924; Lankester, E. Ray (Edwin Ray), Sir, 1847-1929. London, Macmillan and Co.
Size: 1142px × 2189px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
