Some considerations on the phenomena of parasitism amongst protozoa / by E.A. Minchin.
- Minchin, E. A. (Edward Alfred), 1866-1915.
- Date:
- [1910]
Licence: Public Domain Mark
Credit: Some considerations on the phenomena of parasitism amongst protozoa / by E.A. Minchin. Source: Wellcome Collection.
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![some cases the host is another species of Protozoon, into the body of which the intruder penetrates, living either in its cytoplasm or its nucleus. Amoebae are very subject to the attacks of intra-nuclear parasites, and the young stages of many Acinetans are parasitic upon other Infusoria. When the host is one of the Metazoa, the invading organism may be, in like manner, intra-cellular or intra-nuclear in habitat; or it may penetrate into the tissues, living amongst and between the con- stituent cells; or, finally, it may be found in one of the internal cavities of the body, such as the digestive tract, body-cavity, blood or lymph-spaces, urinary organs, etc., either living free in the cavity or attached to the lining epithelium. We may distinguish, in general, two ways in which these parasites may tax the resources of the host. Some of those living in the diges- tive tract may simply absorb the soluble products of digestion occurring there, thus diminishing the nutriment of the host by intercepting its food-supply. Other parasites, in the digestive tract or elsewhere, ravage the very substance of the body of the host, either by devouring cells and tissues, as in the case of the dysenteric amoebae already mentioned ; or, and more usually, by absorbing the vital] fluids and juices of the cells, tissues, or organs into which they penetrate, sapping in many cases the life- springs of the organism that harbours them. As diverse as the modes of parasitism amongst Protozoa are the effects they produce upon their hosts. Some forms of these parasites cause no perceptible disturbance in the well-being of the host ; even when they destroy cells and portions of the tissues, the damage may be slight, and is quickly made good without appreciable harm being done to the host. From this condition of more or less perfect harmlessness there is a continuous grada- tion in the ascending scale of capacity for harmfulness possessed by Protozoan parasites, culminating in species which bring about the death of their hosts with greater or less rapidity. Hence, parasitic Protozoa are commonly characterised as pathogenic, that is to say disease-producing, and non-pathogenic; these two terms imply, however, a distinction which is purely relative, since a ‘‘ disease” may be anything from a slight and transitory](https://iiif.wellcomecollection.org/image/b33439254_0006.jp2/full/800%2C/0/default.jpg)
