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Updated: May 2, 2025
"As several well-marked cases have been recorded with our domestic animals of a relation between the colour of the dermal appendages and the constitution; and it being notorious that there is some limited degree of relation between the colour of the races of man and the climate inhabited by them; the following investigation seems worth consideration.
There seems to be one defect in the papers of both Nussbaum and Smith and Schuster namely, that neither of them mentions or apparently appreciates the fact that the thumb-pads, apart from the dermal glands, consist of horny epidermis developed from the living epidermis beneath. The horny layer is not shown clearly in the figures of Smith and Schuster.
This papilla consists of vascular dermal, i.e. mesodermic tissue, and if the feather is pulled out during growth bleeding occurs. The epidermic horny tube splits posteriorly towards the apex of the feather, and is divided into rachis and barbs, and thus the dermal tissue within, by this time dead and dry, is exposed and is shed.
Lastly, and 9thly, in a cliff of the red clayey bed B, there was a double piece, about three feet long and two wide, of the bony armour of a large Dasypoid quadruped, with the two sides pressed nearly close together: as the cliff is now rapidly washing away, this fossil probably was lately much more perfect; from between its doubled-up sides, I extracted the middle and ungual phalanges, united together, of one of the feet, and likewise a separate phalanx: hence one or more of the limbs must have been attached to the dermal case, when it was embedded.
If, led by the evidence that in animals the amount of covering is in some cases affected by the degree of exposure, it were admitted as imaginable that the development of feathers from preceding dermal growths had resulted from that extra nutrition caused by extra superficial circulation, we should still be without explanation of the structure of a feather.
Cold bathing sends the blood inward partly by the cold which contracts the capillaries of the skin and tissue immediately underlying it, and partly by the pressure of the water over all the dermal surface, quickens the activity of kidneys, lungs, and digestive apparatus, and the reactive glow is the best possible tonic for dermal circulation.
Though we have proof that by rough usage the dermal layer may be so excited as to produce a greatly thickened epidermal layer, sometimes quite horny; and though it is a feasible hypothesis that an effect of this kind persistently produced may be inherited; yet no such cause can explain the carapace of the turtle, the armour of the armadillo, or the imbricated covering of the manis.
For, whilst the horn of the rhinoceros is merely a dermal production, a conglomeration of hairs cemented into one dense mass as hard as bone, and answering the purpose of a defensive weapon, besides being used for digging up the roots on which the animal lives; the horn of the ceratophora is formed of a soft, spongy substance, coated by the rostral shield, which is produced into a kind of sheath.
The assertion with regard to these orders is certainly true, but it should be borne in mind at the same time that the armadillos, which are much more abnormal than are the American anteaters as regards their dermal covering, in their dentition are less so. Again, the Dugong and Manatee are dermally alike, yet extremely different as regards the structure and number of their teeth.
The remains of a second and smaller species of Dendrerpeton, D. Oweni, were also found accompanying the larger one, and still retaining some of its dermal appendages; and in the same tree were the bones of a third small lizard-like reptile, Hylonomus Lyelli, seven inches long, with stout hind limbs, and fore limbs comparatively slender, supposed by Dr.
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