GIARDIA IN ANIMALS 709 



The dimensions of the fixed and stained forms were given as, 13 to 18 

 microns by 6-5 to 12 microns. The living forms appeared somewhat 

 longer, and varied in length from 17 to 20 microns and in breadth from 

 9 to 12 microns. The cysts were 11 to 13 microns in length by 7 to 7-5 

 microns in breadth. Thomson, J. G. (1925), has made the interesting 

 observation that intestinal nematodes {VianeUa sp.) from the same rodents 

 harbour what appears to be the same organism. Two of these rodents 

 died in the Zoological Gardens in London. On examination, hundreds 

 of nematodes heavily parasitized with the flagellate were found, though 

 neither flagellates nor cysts could be discovered in the intestinal contents. 

 The rodents also harboured numerous nematodes of the genus Tricho- 

 strongylus, but in none of these was the flagellate found. It seems highly 

 probable that the flagellate is G. viscacice, which, being ingested by the 

 worms, had found a habitat suitable for its multiplication. It is of 

 interest to note that Brumpt (1910a) has observed that certain Ascaridse 

 parasitic in the colon of horses appear to feed exclusively on the Infusoria 

 — ciliates and flagellates — which live in this part of the intestine. 



G. duodenalis (Davaine, 1875).— This flagellate was first described by 

 Davaine as Hexamita duodenalis. Grassi (1881a) regarded the rabbit form 

 as identical with that of man, a view which was held by Metzner (1901). 

 Bensen (1908) applied to it the name Lamblia cuniculi. The correct name 

 is undoubtedly G. duodenalis. The rabbit flagellate has been studied by 

 Hegner (1922a), who gives the measurements as follows: length, 12-7 to 

 18-7 (average 15-8) microns; breadth, 7-7 to 11-0 (average 9-1) microns. 

 It is thus both broader and longer than G. intestinalis (Figs. 296, 297, B). 

 The two deeply-staining bodies at the base of the tail are described as 

 being often bent and longer than in other species. Fonseca (1915) de- 

 scribed a form which he regarded as this species in Coendu villosus, as 

 also in the rabbit of Brazil. Hegner (1922a) believes that possibly he 

 was dealing with a distinct species, 



G. canis Hegner, 1922. — This form, which was first noted by Grassi 

 (1881a), was again mentioned by Grassi and Schewiakoff (1888) and by 

 Janowski (1897). The writer has seen it in dogs in England. Hegner 

 (1922a) states that it has a characteristically broad anterior end 

 (Fig. 296, e). It varies in length from 11-9 to 17-0 microns (average 13-8) 

 and in breadth from 7-6 to 10-2 microns (average 8-5). 



Giardia cati Deschiens, 1925. — This form was first seen by Grassi 

 (1881a), and was named by Deschiens (1925). Later, Hegner (1925a) 

 gave the name G. felis to a parasite of the cat in America. Hegner's 

 flagellate, which may not be the same as the one studied by Deschiens, 

 measured from 10-5 to 17-5 microns in length and from 5-25 to 8-75 microns 

 in breadth. The cysts measured 10-5 by 7-35 microns. In the writer's 



