United States or Oman ? Vote for the TOP Country of the Week !
In the harlequin fetus the whole surface of the body is thickly covered with fatty epidermic plates, about 1/16 inch in thickness, which are broken up by horizontal and vertical fissures, and arranged transversely to the surface of the body like a loosely-built stone wall. After birth these fissures may extend down into the corium, and on movement produce much pain.
In the further course of development the epiblast becomes the ectoderm or epidermic layer of the body; the hypoblast becomes the epithelium of the middle portion of the alimentary canal; and the mesoblast gives rise to all the other tissues, except the central nervous system, which originates from an ingrowth of the epiblast.
The exodus from the mortuary tabernacle was made through the round holes wherewith the skin is pierced. Those holes are the worms' work: of that there is no doubt; and yet we have lately seen the mothers refuse as a bed for their eggs any part whereat the flesh is protected by a skin of some thickness. The reason is the failure of the pepsin to act on epidermic substances.
When we come to the higher Metazoa, in which the sensory functions and their organs are more advanced, we find a division of labour among the ectodermic cells. Groups of sensitive nerve cells separate from the ordinary epidermic cells; they retire into the more protected tissue of the mesodermic under-skin, and form special neural ganglia there.
I doubt if there is a single instance in which the male bird takes up a position to present his ornamental plumage to the sight of the female without a special erection and movement of the feathers themselves. Such a stimulation must affect the living epidermic cells of the feather papilla.
He does not attempt to show how the use or employment of the head leads to the development of these outgrowths of bone and epidermic horn, but attributes their development in stags and bulls to an 'interior sentiment in their fits of anger, which directs the fluids more strongly towards that part of their head.
In their case the hypothesis has lately been advanced on the strength of very extensive research, especially by Friedrich Maurer, that they have been evolved from the cutaneous sense-organs of amphibian ancestors by modification of functions; the epidermic structure is very similar in both in its embryonic rudiments.
Masses of epidermic scales may form around the broken ends of the feathers. The diagnosis can be confirmed by examining the skin lesions and finding the mite. A post-mortem examination of a fowl that has died of this disease shows the mites on the surface of the lining membrane of the air-sacs. They appear as a white or yellow dust.
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.
Similarly is it with the organs for smelling and hearing. These, too, begin as sacs formed by infoldings of the epidermis; and while their parts are developing they are joined from within by nervous structures which were themselves epidermic in origin. How are we to interpret these strange transformations?
Word Of The Day