The parasitic hypothesis postulates the invasion of a parasite from without, thus making a new growth an infective process.
Thus we get a complete scientific demonstration of the causation of malaria in three stages: (1) the discovery of the parasite by Laveran; (2) its life-history in the human host and connexion with the fever demonstrated by the Italian observers; (3) its life-history in the alternate host, and the identification of the latter with a particular species of mosquito by Ross and Manson.
In 1898 it was conclusively shown in Italy that if a mosquito E of the Anopheles variety bites a person suffering from malaria, and is kept long enough for the parasite to develop in the salivary gland, and is then allowed to bite a healthy person, the latter will in due time develop malaria.
The itch-insect (Sarcoptes scabiei) is a well-known human parasite, so minute that it was not discovered until the end of the 18th century, and " the itch " was treated medicinally as a rash.
For some of these, as redwater (pyrosoma), antidotes are already found; for others, as for Texas fever - of which the parasite is unknown, but the mode of its transmission, by the mosquito, discovered (Finlay-Reed) - preventive measures are reducing the prevalence.
Man himself, as well as other mammals, is the intermediate host of the dangerous parasite, Taenia echinococcus, in countries where cleanliness is neglected; the pig is the host of Taenia solium, and other cases may be seen from the table at the end of this article.
In the case of filariasis due to Filaria bancrofti, which is common throughout the Tropics, the embryos of the parasite are disseminated by various Culicinae and Anophelinae (Culex pipiens in Queensland; C. fatigans in the West Indies; Myzomyia rossii in India; Pyretophorus costalis in a large portion of tropical Africa; &c.).
The old age of Trembecki appears to have been ignoble and neglected; he had indeed "fallen upon evil days and evil tongues"; and when he died at an advanced age all the gay courtiers of whom he had been the parasite were either dead or had submitted to the Muscovite yoke.
In dealing with disease-causing forms, the more narrowly the original source of the parasite concerned is defined, the closer do we get to the true vertebrate host or hosts.
All the members of this order are parasitic on aquatic vertebrates and in rare cases derive their food from a vertebrate host indirectly by means of another invertebrate parasite (e.g.
It has been shown that this parasite feeds upon the blood, not the bile of its host, though it occurs mainly in the bile ducts.
If such a general parasite carries its activities farther, every cell may be killed and the plant forthwith destroyed e.g.
It must not be overlooked that the living cells of the plant react upon the parasite as well as to all external agencies, and the nature of disease becomes intelligible only if we bear in mind that it consists in such altered metabolismdeflected physiologyas is here implied.
In scabies (itch) it is the best remedy, killing the male parasite, which remains on the surface of the skin.
Demonstrated by a series of accurate investigations, contributed by many workers, that malaria is caused by a microscopic parasite in the blood, into which it is introduced by the bites of certain species of mosquito.
The discovery of the parasite of malaria by Laveran, and of the method by which it gains entrance to the human body, through the bite of a particular variety of mosquito, by Manson and Ross, promises much in the way of eradication of the disease in the future.
If the attack of a parasite is met by the formation of some substance in the protoplasm which is chemo- tactically repulsive to the invader, it may be totally incapable of penetrating the cell, even though equipped with a whole armoury of cytases, diastatic and other enzymes, and poisons which would easily overcome the more passive resistances offered by mere cell-walls and cell-contents of other plants, the protoplasm of which forms bodies chemotactically attractive to the Fungus.
In 1894 (Sir) David Bruce discovered the celebrated South African parasite (T.
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,.
It is one thing to protect individuals from mosquito bites, another to prevent the propagation of the parasite in a whole community.
By this time the embryo has all the organs of the adult perfected save only the reproductive; these develop only when the first host is swallowed by the second or final host, in which case the parasite attaches itself to the wall of the alimentary canal and becomes adult.
In the case of oxen the alternate host of the parasite is a special tick (Smith and Kilborne).
1845) discovered the parasite of malaria, and truly conceived its relations to the disease; thus within two years were made two discoveries either of which was sufficient to make the honour of a century.
In the treatment of a case where the parasite is already present, for two days previous to the employment of a vermifuge a light diet should be given and the bowels moved by a purgative.
18, Bureau of Plant Industry, U.S. Department of Agriculture), who attributes it not to any specific parasite but to a disturbance of the normal physiological activity of the cells.
Speaking generally each species of parasite has a particular host, upon the blood of which it nourishes itself and matures its reproductive organs.
In the case of the pearl oyster this parasite is a cestode larva, but in the less valuable but no less genuine pearl produced by Mytilus, &c., the nucleus is a Trematode-larva (Jameson).
The attention of birds is speedily attracted to the snail by this appearance and by the peculiar movements which the worm executes, and the passage of the parasite into its final host is advantageously effected.
It is important to note that although sleeping sickness (of which the chief foci are at present the Congo Free State and Uganda) has hitherto been associated with one particular species of Glossina, it has been shown experi mentally both that other tsetse-flies are able to transmit the parasite of the disease, and that G.
It shows how a bold and p lausible adventurer, aided by the profligacy of a parasite, the avarice and hypocrisy of a confessor, and a mother's complaisant familiarity with vice, achieves the triumph of making a gulled husband bring his own unwilling but too yielding wife to shame.
Brucii, the nagana parasite in G.