Among recent advances having medical import in our knowledge of the Nematodes, the chief are those dealing with the parasites of the blood.
Gunther, " On the Structure and Affinities of Mnestra parasites Krohn; with a revision of the Classification of the Cladonemidae," Mitt.
These enenlies are as a rule so conspicuous that we do not look on their depredations as diseases, though the gradual deterioration of hay under the exhausting effects of root-parasites like Rhinanthus, and the onslaught of Cuscuta when unduly abundant, should teach us how unimportant to the definition the question of size may be.
He creates the parasites that are vamps, which then kill humans.
C. Claus, " Ober die Struktur der Muskelzellen and fiber den Korperbau von Mnestra parasites Krohn," Verhandl.
Hales (1727I 733) discussed the rotting of wounds, cankers, &c., but much had to be done with the microscope before any real progress was possible, and it is easily intelligible that until the theory of nutrition of the higher plants had been founded by the work of Ingenhouss, Priestley and De Saussure, the way was not even prepared for accurate knowledge of cryptogamic parasites and the diseases they induce.
On the 6th of November in that year he plainly saw the living parasites under the microscope in the blood of a malarial patient, and he shortly afterwards communicated his observations to the Paris Academie de Medecine.
As an appendix to the Oligochaeta, and possibly referable to that group, though their systematic position cannot at present be determined with certainty, are to be placed the Bdellodrilidae (Discodrilidae auct.), which are small parasites upon crayfish.
All the species are usually infested with Cercariae and Rediae, the larval forms of Trematode parasites of vertebrates.
The parasites, which cling to the intestinal mucous membrane, draw their nourishment from the blood-vessels of their host, and as they are found in hundreds in the body after death, the disorders of digestion, the increasing anaemia and the consequent dropsies and other cachectic symptoms are easily explained.
Of all parasites the one which by its mere presence is the most dangerous is the larva of Taenia echinococcus.
The term "biting-lice" is sometimes given to these parasites, in allusion to the mandibulate character of their mouth-parts, which serves to distinguish them at once from the true lice of the order Rhynchota in which the jaws are haustellate.
The presence of these parasites seems at times to have little effect on the host, and men in whose system it is calculated there are some 40-50 million larvae have shown no signs of disease.
The effects of these parasites have been mistaken for those of disease.
Mechanical injury from without, and against the entry of smaller parasites, such as fungi and bacteria, but also and especially to prevent the evaporation of water from within.
Fungal and phanerogamic parasites can make no use of stich substances as carbon dioxide, but draw elaborated products from the bodies of their hosts.
It was formerly the custom to regard as parasites all those pants which inserted roots or root-like organs into the tissues of other plants and absorbed the contents of the latter.
Many larvae of beetles, moths, &c., bore into bark, and injure the cambium, or even the wood and pith; in addition to direct injury, the interference with the transpiration current and the access of other parasites through the wounds are also to be feared in proportion to the numbers of insects at work.
Plants as agents of damage and disease may be divided into those larger forms which as weeds, epiphytes and so forth, do injury by dominating and shading more delicate species, or by gradually exhausting the soil, &c., and true parasites which actually live on and in the tissues of the plants.
Numerous Fungi, though conspicuous as parasites, cannot be said to do much individual injury to the host.
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.
Roots are often flattened, twisted and otherwise distorted by mechanical obstacles; stems by excess of food in rich soils, the attacks of minute parasites, overgrowth by climbing plants, &c. Leaves are especially apt to vary, and although the formation of crests, pitchers, puckers, &c., must be put down to the results of abnormal development, it is often difficult to draw the line between teratological and merely varietal phenomena.
Cactaceae, Euphorbiaceae), of parasites, and of saprophytes.
The labours of Golgi, Marchiafava, Celli and others established the nature of the parasite and its behaviour in the blood; they proved the fact, guessed by Rasori so far back as 1846, that the periodical febrile paroxysm corresponds with the development of the organisms; and they showed that the different forms of malarial fever have their distinct parasites, and consequently fall into distinct groups,.
Three distinct parasites, corresponding with the tertian,.
With regard to the parasites, which are the actual cause of malaria in man, an account of them is given under the heading of Parasitic Diseases, and little need be said about them here.
Apparently the parasites may remain quiescent in the blood for years and may cause relapses by fresh sporulation.
Birds are subject to malaria, which is caused by blood parasites akin to those in man and having a similar life-history.
Many bird parasites belonging to the Rippoboscidae have naturally been carried about the world by their hosts, while other species, such as the house-fly, blow-fly and drone-fly, have in like manner been disseminated by human agency.
These parasites damage the hide, B FIG.
To begin with, 1 Though not relating exactly to our present theme, it would be improper to dismiss Nitzsch's name without reference to his extraordinary labours in investigating the insect and other external parasites of birds, a subject which as regards British species was subsequently elaborated by Denny in his Monographia Anoplurorum Britanniae (1842) and in his list of the specimens of British Anoplura in the collection of the British Museum.
(Monograph), and The Animal Parasites of Man (London, 1906); W.
Hornell, "Parasites of the Pearl Oyster," Report on the Pearl Oyster Fisheries of the Gulf of Manaar, The Royal Society (1904), pt.
The fact of this increased leucocytic activity during the early stages, or the whole course of infection by Cestodes, is indirect proof that these parasites do normally discharge toxic substances into their hosts.
- (I) Leuckart, The Parasites of Man (Edinburgh, 1886); (2) Braun, The Animal Parasites of Man (London, 1906); (3) Id., " Cestodes " in Braun's Klassen u.
(1894); (4) Shipley and Fearnsides, " Effects of Parasites," Journ.
Of these the best known were: the Kolakes, in which he pilloried the spendthrift Callias, who wasted his substance on sophists and parasites; Maricas, an attack on Hyperbolus, the successor of Cleon, under a fictitious name; the Baptae, against Alcibiades and his clubs, at which profligate foreign rites were practised.
- The following works are the most important: Denny, Monographia Anoplurorum Britanniae (London, 18 43); Giebel, Insecta Epizoa (which contains the working-up of Nitzsch's posthumous materials; Leipzig, 1874); van Beneden, Animal Parasites (London, 1876); Piaget, Les Pediculines (Leiden, 1880); Megnin, Les Parasites et les maladies parasitaires (Paris, 1880); Neumann, Parasites and Parasitic Diseases of Domesticated Animals (1892); Osborn, Pediculi and Mallophaga affecting Man and the Lower Animals (Washington, 1891; U.S. Dept.
It is invariably the result of some cause acting generally, such as renal disease, valvular defect of the heart, or an impoverished state of the blood; while a mere oedema is usually dependent upon some local obstruction to the return of blood or lymph, or of both, the presence of parasites within the tissue, such as the filaria sanguinis hominis or trichina spiralis, or the poisonous bites of insects.
The toxic actions produced in continued fevers, in certain chronic diseases, and by intestinal parasites largely aid in producing degeneration, emaciation and atrophy.
Many cancer-parasites have been described in cancerous growths, including bacteria, yeasts and protozoa, but the innumerable attempts made to demonstrate the causal infective organism have all completely failed.
The parasites thrive in an environment of dirt, and the main lines of precaution are those dictated by sanitary science.