. Evolution and disease . wo in circumference. Itwas situated in the same lineposteriorly to the normal was structurally a wart. Thatcutaneous horns should arise inoxen and other hollow-hornedruminants {Cavicornid) need notsurprise us when we reflect thatthe corneous caps of their naturalhorns are modified portions ofthe integument. Birds not infrequently exhibit wart-horns of this character, and an example growing from the leg of an oyster-catcher is shown in „ . ^, , t rs . fig- 6. Such horns, whenever Fig. 6.—The leg of an Oyster ° Catcher {Hcematopiis ostra- they have been observe
. Evolution and disease . wo in circumference. Itwas situated in the same lineposteriorly to the normal was structurally a wart. Thatcutaneous horns should arise inoxen and other hollow-hornedruminants {Cavicornid) need notsurprise us when we reflect thatthe corneous caps of their naturalhorns are modified portions ofthe integument. Birds not infrequently exhibit wart-horns of this character, and an example growing from the leg of an oyster-catcher is shown in „ . ^, , t rs . fig- 6. Such horns, whenever Fig. 6.—The leg of an Oyster ° Catcher {Hcematopiis ostra- they have been observed in birds, /fo?/i) with a large wart-liorn. r n ,i 1 c • lollow the usual course of aviandermal organs in general, and are shed with eachmoult and reproduced with the new feathers. Thehorn on the leg of the oyster-catcher when comparedwith the size of the bird is ver) large. It is representedone-fourth its natural size. The shedding of pathological cutaneous horns andtheir subsequent reproduction has more than one. INTRO D UCTION. II physiological type. Among birds the horned puffin{Fratercida corniculata) will be selected. Growing from the upper eyelid of this bird is aslender, pointed, black-coloured horn, which in thespecimen from which the drawing (fig. 7) was made,measured eighteen millimetres in length : there is alsoa thin horny scale connected with the lower lid. Inthe adult bird it is stated that these horns are shed andreproduced annually.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectabnormalitieshuman
