EN
Referring to the studies of E. N. Pawłowski and W. G. Gniezdiłow (1939, 1949, 1953) the author examined this problem in the natural infection of dogs: 40 animals were used for experiments. The results obtained show that D. caninum is mainly localized in the iliac intestine, but with the increasing number of populations the parasites were also found to occupy the posterior segment of the jejunum (diagram). The mean length and wet weight of the population are inversely proportional to the mean length and wet weight of individuals; this correlation is determined by the number of population (table 1). When the numerical value of the population was low the differentiation of the parasites was but slight, its augmentation being accompanied by increase in young and reduction in mature forms (table 2). There were also differences in the appearance and condition of parasites depending on whether they derived from numerically low or high populations.