GIARDIA INTESTINALIS 701 



and Hegner (1922a) maintain that species may be distinguished by the 

 average dimensions of a number of individuals, and they illustrate in a 

 graphic manner the measurements which are necessary for identification 

 (Fig. 296). 



Reuling and Rodenwaldt (1921) have attempted to revive the genus 

 Lamblia by suggesting that G. agilis, described by Kunstler (1882) from 

 tadpoles, differs sufficiently from the other forms to justify their in- 

 clusion in a separate genus, Lamblia. The tadpole parasite is a long 

 narrow organism with a small sucking disc (Fig. 298), while all other 

 forms rarely have a length as much as twice that of their breadth. 

 They believe that the generic name Giardia should be retained for the 

 narrow form, of which there is the one species, G. agilis Kunstler, 1882. 

 The broader forms, which include all the others, are to be placed in 

 Blanchard's genus, Lamblia, the type species being the human parasite, 

 L. intestinalis (Lambl, 1859). The authors seem inclined to this view 

 rather from a desire to retain the name Lamblia for the human parasite 

 than from conviction that the differences between the two forms are of a 

 generic value. It does not seem to the writer that matters are assisted in 

 any way by splitting into two sub-genera the very compact and uniform 

 genus, Giardia, merely because certain forms in the tadpole are narrower 

 than those in other animals. As pointed out by Hegner (1922), the 

 differences described are certainly not of generic value. 



The various forms of Giardia which are known are invariably inhabi- 

 tants of the small intestine. In mammals they are to be found in the 

 upper parts of the small intestine and duodenum. When they occur 

 lower down, it is probable that their appearance is accidental. They can 

 be studied in sections of the intestine, and are often found in large numbers 

 in the tubules of the secreting glands, a fact which probably aft'ords an 

 explanation of the difficulty in getting rid of an infection in human beings 

 by the administration of intestinal disinfectants. 



GIARDIA IN MAN. 



Giardia intestinalis (Lambl, 1859). — As noted above, this flagellate was 

 named Cercomonas intestinaUs by Lambl (1859). Diesing (1851) had. liowever, 

 given this name to a flagellate which Ehrenberg had previously described as Bodo 

 intestinalis. As pointed out by Dobell (1909), Diesing was in error in so doing, as 

 Ehrenberg's flagellate was not a Cercomonas, but probably a Hexamita. Hence, 

 DobeU concludes that Lambl's specific name is still available for the human Giardia. 

 Kofoid (1920), believing that Lambl's name was not available, adopted Grassi's 

 name, and referred to the human form as 6. enterica Grassi, 1881 ; while Simon (1922) 

 states that Stiles has shown that the name G. enterica, which is in reality a synonym 

 of G. muris, cannot be employed, and proposes to adopt the name G. lamblia StUes, 

 which was put forward in a paper by Kofoid and Christiansen (1915). If the rules 

 of uomenclaturo are strictly adhered to, Lambl's specific name intestinalis cannot 



