Under the head of malformations we place cases of atrophy of parts or general dwarfing, due to starvation, the attacks of Fungi or minute insects, the presence of unsuitable food-materials and so on, as well as cases of transformation of stamens into petals, carpels into leaves, and so forth.
The essential feature of the asymmetry of Gastropoda is the atrophy or disappearance of the primitively left half of the circumanal complex (the right half in sinistral forms), including the gill, the auricle, the osphradium, the hypobranchial gland and the kidney.
Many Opisthobranchia have by a process of atrophy lost the typical ctenidium and the mantleskirt, and have developed other organs in their place.
The variety of special developments of structure accompanying the atrophy of typical organs in the Opisthobranchia and general degeneration of organization is very great.
They will hold their arms over their heads until the muscles atrophy, will keep their fists clenched till the nails grow through the palms, will lie on beds of nails, cut and stab themselves, drag, week after week, enormous chains loaded with masses of iron, or hang themselves before a fire near enough to scorch.
The atrophy of the Ottoman sea-power had left the archipelago at the mercy of the Greek war-brigs; piracy flourished; and it became essential in the interests of the commerce of all nations to make some power responsible for the policing of the narrow seas.
The spinning appendages migrate to the posterior end of the opisthosoma and take up a position close to the anus; the inner branches of the anterior pair either atrophy or are represented homogenetically by a plate, the cribellum, or by an undivided membranous lobe, the colulus.
Thus the occurrence of blind animals in caves and in the deep sea was a fact which Darwin himself regarded as best explained by the atrophy of the organ of vision in successive generations through the absence of light and 1 Weismann, Vererbung, &c. (1886).
From atrophy of their roots, caused by the pressure of the growing permanent teeth, the " milk teeth " in children become loose and are cast off.
General atrophy or emaciation is brought about by the tissues being entirely or partially deprived of nutriment, as in starvation, or in malignant, tubercular, and other diseases of the alimentary system which interfere with the proper ingestion, digestion or absorption of food material.
The loss of an eye will be followed by atrophy of the optic nerve; the tissues in a stump of an amputated limb show atrophic changes; a paralysed limb from long disuse shows much wasting; and one finds at great depths of the sea fishes and marine animals, which have almost completely lost the organs of sight, having been cut off for long ages from the stimuli (light) essential for these organs, and so brought into an atrophic condition from disuse.
Atrophy can be caused by overwork.
Increased work thrown on to a tissue may produce hypertrophy, but, if this excessive function be kept up, atrophy will follow; even the blacksmith's arm breaks down owing to the hypertrophic muscle fibres becoming markedly atrophied.
In other cases the reproductive cells perhaps pass out by the atrophy of the polypide, whereby the body-cavity may become continuous with the exterior.
The continued use of large doses of alcohol produces chronic gastritis, in which the continued irritation has led to overgrowth of connective tissue, atrophy of the gastric glands and permanent cessation of the gastric functions.
When, for instance, the axons of the ganglion cells of the retina are severed by section of the optic nerve, and thus their influence upon the nerve cells of the visual cerebral centres is set aside, the nerve cells of those centres undergo secondary atrophy (Gadden's atrophy).
In Dictyota the unfertilized oosphere is found to be capable of undergoing a limited number of divisions, but the body thus formed appears to atrophy sooner or later.
They agree with the true crabs in not having appendages (uropods) to the sixth segment of the pleon, the atrophy being complete in the Homolidae and Homolodromiidae, whereas in the Dromiidae and Dynomenidae a pair of small plates appear to be vestiges of these organs.
He entered the lists boldly against the materialism of " Stoff and Kraft," and avowed himself a Christian believer, whereupon he lost the countenance of a number of his old friends and pupils, and was unfeelingly told that he was suffering from an " atrophy of the brain."
Observations were made on the connexion between thyroid gland and myxoedema, which appeared to show that this disease was dependent upon atrophy of the gland.
Mention should also be made of the partial or complete atrophy of the eyes in many Crustacea which live in darkness, either in the deep sea or in subterranean habitats.
In other species the large individuals have become purely female by atrophy of the male organs, and are entirely dependent on the dwarf males for fertilization.
It was admitted that these elements might atrophy, or be displaced, or be otherwise obscured; but their complete and symmetrical disposition was regarded as typical and original.
Known Echinoderms show the following features, imagined to be due to an ancestral pelmatozoic stage :- Increase in the coelomic cavities of the left side, and atrophy of those on the right; the dextral coil of the gut, recognizable in all classes, though often obscured; an incomplete secondary bilateralism about the plane including the main axis and the water-pore or its successor, the madreporite, often obscured by one or other of various tertiary bilateralisms; the change of the hydrocoel into a circumoral, arcuate or ring canal; development through a freeswimming, bilaterally symmetrical, ciliated larva, of which in many cases only a portion is transformed into the adult Echinoderm (where care of the brood has secondarily arisen, this larva is not developed).
- Pelmatozoa in which five (by atrophy four) epithecal ciliated grooves, lying on a lancet-shaped plate (?
- Crinoidea in which the base consists of BB and IBB, the latter being liable to atrophy or fusion with the proximale, but the aboral prolongations of the chambered organ are always radial; new columnals may or may not be introduced at the proximal end of the stem.