That special trophic nerves, however, exist throughout the body, seems to be a myth.
Trophic and nervous conditions sometimes cause localized deficiency of pigment which produces white areas in the skin.
The acute bed-sore is, in some cases, a true trophic lesion occurring, as it may, on parts not subjected to continuous pressure or irritation.
Trophic disturbance in the nutrition of the skin may be so great that a slight degree of external pressure or irritation is sufficient to excite even a gangrenous inflammation.
It forms the trophic centre of Solidarity the cell, just as the nucleus-containing part of every cell is the trophic centre of the whole cell.
In diameter, with little yolk, and the embryos provided with large trophic vesicles (Willey).
It is much more likely, as Verworn alleges, that the nerves which influence the characteristic function of any tissue regulate thereby the metabolism of the cells in question - in other words, that every nerve serves as a trophic nerve for the tissues it supplies.
In the Telosporidia (comprising the Gregarines, Coccidia and Haemosporidia), sporulation does not begin until the close of the vegetative or trophic period, i.e.
In the New Britain species the egg is still smaller (I mm.), and there is a large trophic vesicle.
This trophic influence which one neuron exerts upon others, or upon the cells of an extrinsic tissue, such as muscle, is exerted in that direction which is the one normally taken by the natural nerve impulses.
The common variety of bed-sore is the result of continuous pressure on and irritation of the skin, the vitality and resisting power of which are lowered by a lesion of the cord cutting off the trophic supply to the skin affected.
If, on the other hand, any pathogenic organisms be present the results are disastrous because the tissue, deprived of its nervous trophic supply, has greatly lessened resistance.
A Trypanosome always possesses two distinct nuclear bodies, one the trophonucleus, regulating the trophic life of the cell, the other, the kinetonucleus, directing its locomotor activities.
The mesoblast multiplies its cells, which become partly muscular and partly skeleto-trophic. Centro-dorsally now appears the embyronic shell-gland.
In addition to the trophic influence exerted by each part of the neuron on its other parts, notably by the perikaryon on the cell branches, one neuron also in many instances influences the nutrition of other neurons.
The bed-sores which follow paralysis of the limbs are often quoted as proof of the direct trophic action of the nerve-supply upon the tissues, yet even here the evidence is somewhat contradictory.