They are due to hypertrophy of young tissues, which may undergo profound alterations subsequently, and occur on all parts of the plants.
They often cause a considerable hypertrophy of the tissue.
The swellings have been found to be due to a curious hypertrophy of the tissue of the part, the cells being filled with an immense number of minute bacterium-like organisms of V, X or Y shape.
It may be advisable to define exactly what is meant by " hypertrophy," as the term is often used in a loose and insignificant sense.
These are: (I) That the green plant is so stimulated by the symbiotic association which leads to the hypertrophy, that it is able to fix the nitrogen or cause it to enter into combination.
Similarly with Anemone infested with Puccinia and Vacciniusn with Catyptospora, and many other cases of deformations due to hypertrophy or atrophy.
The now well-known fact that small doses of poisonous substances may act as stimuli to living protoplasm, and that respiratory activity and growth may be accelerated by chloroform, ether and even powerful mineral poisons, such as mercuric chloride, in minimal doses, offers some explanation of these phenomena of hypertrophy, wound fever, and other responses to the presence of irritating agents.
Botrytis, Ergot, &c. Now it is clear that if an organism gains access to all parts of a plant, and stimulates all or most of its cells to hypertrophy, we may have the latter behaving abnormallyi.e.
But even when inside it does not follow that the Fungus can kill the cell, and many cases are known where the Fungus can break throtigh the cells first lines of defence (cell-wall and protoplasmic lining); but the struggle goes on at close quarters, and various degrees of hypertrophy, accumulation of plastic bodies or secretions, discolorations, &c.,, indicate the suffering of the still living cell.
Cecidia or galls arise by the hypertrophy of the subepidermal cells of a leaf, cortex, &c., which has been pierced by theovipositor of an insect, and in which the egg is deposited.
Although an integral portion of the gut, it has ceased to assist in alimentation, its epithelium undergoes vacuolar differentiation and hypertrophy, and its lumen becomes more or less vestigial.
Whilst absolutely contra-indicated in all cases of valvular disease, it is of value in cases of cardiac hypertrophy with over-action.
For this reason it is used to remove corneal opacities, deafness due to thickening of the membrane, stricture of the oesophagus and hypertrophy of the pylorus, it has also been successful in the treatment of adhesive parametritis.
Irritation and hypertrophy of cells are common signs of the presence of parasites, as ovinced by the numerous malformations, galls, witches-brooms, &c., on diseased plants.
Mere enlargement of an organ does not imply that it is in a state of hypertrophy, for some of the largest organs met with in morbid anatomy are in a condition of extreme atrophy.
The term hypertrophy is used when the individual tissue elements become bigger to meet the demands of greater functional activity; hyperplasia, if there is an increase in the number of these elements; and pseudo-hypertrophy, when the specific tissue element is largely replaced by another tissue.
True hypertrophy is commonly found in the hollow muscular organs such as the heart, bladder and alimentary canal.
Examples of physiological hypertrophy are found in the ovaries, uterus and mammary glands, where there is an increased functional activity required at the period of gestation.
Local hypertrophy may also be due to stimulation resulting from friction or intermittent pressure, as one may see in the thickenings on the skin of the artisan's hands.
A certain consequence of its use is to cause or increase cardiac hypertrophy - a condition which has its own dangers and ultimately disastrous consequences, and must never be provoked beyond the positive needs of the case.
In post-mortem examination, the most obvious pathological lesion is hypertrophy of the spleen, which may be very pronounced; the lymphatic glands in the neck, inguinal region, &c., are also often greatly swollen.
Internal causes of extinction are to be found in exaggeration of body size, in the hypertrophy or over-specialization of certain organs, in the irreversibility of evolution, and possibly, although this has not been demonstrated, in a progressive reduction of variability.
The exciting cause of the hypertrophy, in the case of the typical galls, appears to be a minute quantity of some irritating fluid, or virus, secreted by the female insect, and deposited with her egg in the puncture made by her ovipositor in the cortical or foliaceous parts of plants.
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.