Several workers have observed that in a cestode infection the size of the worms is, roughly speaking, inversely proportional to the number of worms in the given infection. This has been called the “crowding effect.” Woodland (1924), Shorb (1933), and Hunninen (1935) demonstrated this phenomenon in rats and mice infected with Hymenolepis nana. Chandler (1939) and Hager (1941) reported this effect in studies on Hymenolepis diminuta. Reid (1942) obtained similar results with Raillietina cesticillus. Reid’s data may be somewhat more accurate from a quantitative standpoint since he used weight as a measure of size, whereas previous workers relied on linear measurements as criteria. Wardle and Green (1941), studying the rate of growth of Diphyllobothrium latum, used the weight-length ratio as an index of average cross sectional area. This seems to be a valid approach to problems of this type.

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