Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)

100, 200, 500, 1200 or 2000 larvae. Egg output was assessed by faecal examination every "two days while worm counts and sex ratio determinations were made on groups of 5 rats that were killed on days 5, 10, 15, 20, 25 and 35 after infection.At dissection the small intestine was divided into 5 sections of equal length and the number and sex of the nematodes determined per section. Results The dynamics of egg output are shown in Table 1, and data relating to worm numbers are given in T a b í e 2. Egg output

. Fig. 1 shows that in every group egg output began on the sixth day. After the peak on days 10-12, the level of egg output diminished gradually in groups infected with 25-200 larvae, and some eggs were found even on day 30. On the other hand, in groups infected with 500-2000 larvae, the number of eggs decreased rapidly and no egg production could be demonstrated by days 20-22. This finding, showing a correlation between size of infection and egg output, agrees with the observations of other authors (l, 5, 10). Localization of the worms

. The smaller Nematode populations were found in the first or first two sections of the small intestine, and the larger populations in the first four sections. The fifth section was free of parasites even after a 2000 larval infection. These findings are in accord with BRAMBELL'

s (2) observations

. Number of worms

. In all groups the number of worms decreased after days 5-10. However, the rate of decrease was greater in groups infected by larger numbers of larvae (Table 2). Owing to the mofe rapid elimination of the larger populations, an essentially uniform residual population was found on days 25-35 in the groups infected with various doses of larvae.