GIARDIA IN ANIMALS 



707 



avocetta). Later (1923), he recorded as G. ardece flagellates which he found 

 in Ardea cinerea, A. rubra, Nycticorax griseus, and Pelegadis falcinellus. 



Kiinstler (1882), who founded the genus Giardia, described as G. agilis 

 a form which occurs in the tadpole. Observing flagellates, which appeared 

 to be of a different type in tadpoles, Kunstler and Gineste (1907) proposed 

 to name two new species, G. gracilis and G. alata. Alexeieff (1914) expressed 

 it as his opinion that all the forms belonged to the one species, G. agilis, 

 a view which is shared by Hegner (1922), who has given a description of 

 the tadpole flagellate. 



As already remarked, apart from G. agilis, which is distinctly elongate, 

 the various species of Giardia are very much alike in appearance, and the 

 various morphological differences which have been described are quite 



Fig. 297. — Various Species of Giardia of Mammals ( 

 A. G. miiris of the mouse. B. G. duodenalis of the rabbit. 



,300). (Original.) 

 C. G. sp. from the cat. 



inconstant and cannot be employed for the separation of species. If, 

 however, a large number of flagellates from a human case be examined and 

 compared with those occurring in rats or mice, the impression is gained 

 that the human form is longer in proportion to its breadth than the mouse 

 form. By actual measurement this is shown to be the case, and it is not 

 improbable that a comparison of the average dimensions of the forms from 

 other animals may show that constant differences in size occur, as Simon 

 and Hegner maintain. Such a method of identifying species is, however, 

 a long and tedious process. 



Giardia muris (Grassi, 1879). — This species was first seen by Grassi 

 (1879«, 1881a), who regards it as identical with the human form (Figs. 296, 

 c, and 297, A). It was described by the writer (1907), and by Bensen (1908) 

 and Kofoid and Christiansen (1915a). Bensen believed that it could be 

 distinguished from other forms by certain morphological characters, 

 especially those of the two deeply-staining bodies which lie dorsal to the 



