Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 6. (Budapest, 1973)
a) As to the taxonomic structure, it is obvious that under conditions of the European part of the Palaearctic region M. arvalis is parasitized by 4 classes of helminths ,namely Trematoda, Cestoda » Hematoda and Acanthocephala . Most numerous are Cestoidea and Nematoda. The specimens belonging to Trematoda and Acanthocephala were found only occasionally and rarely. b) As to the biological structure, the geohelminths, pseudogeohelminths and ageohelminths prevail in our material. All these species develop without an intermediate host. This finding is fully consistent with the data on the food of M.arvalis. H0LIS0VÁ (1959) records herbs, grass and non-green parts of plants as the main food of M. arvalis. The animal proportion of the food (where the possible intermediate hosts of parasites may be present) is small and constitutes only a low percentage. According to the results available , the helminth species which infect M. arvalis without intermediate hosts (especially Nematoda) have in general a much higher incidence and intensity of infection than those which infect M. arvalis with the help of intermediate hosts (Table 3). c) The topical structure is characterized by the prevalence of intestinal species. We have recovered specimens belonging to all classes of parasitic helminths ,namely Trematoda, Cestoda j Nematoda and Acanthocephala. Most of the worms were located in the small intestine, and only a few species were found in the caecum (e .g . nematodes of the genus Trichocephalus , the cestode Paranoplocephala brevis and the trematode Notocotylus noyeri ). As to the number of helminth species, some species were occasionally found in the cysts on the stomach wall (larval stages of nematods of the genus Heligmosomum ) or in the cysts on the wall of the intestine (larval stages of the nematodes of the genus Porrocaecum ) . In the tissues of M. arvalis the larval stages of the nematode Trichinella spiralis were found, while in the liver and in the body cavity only the larval stages of cestodes parasitize . d) In case of the quantitative structure it was most difficult 140
