702 ORDEE: DIPLOMONADIDA 



be employed for the human Oiardia, since the name Cercomonas intestinalis was 

 already given to another flagellate (Hexamita of frogs, Diesing, 1851), when Lambl 

 used it in 1859 for the Giardia of man. As Boeck and Stiles (1923) point out, it 

 appears that the correct name for the human Giardia will have to be Giardia lamblia 

 Stiles, 1915. The better-known name, G. intestinalis, will, however, be retained here. 



This species is a common intestinal parasite of man, and has a workl- 

 wide distribution. It lives in the upper parts of the small intestine, thus 

 differing from the other intestinal Protozoa of man, which are inhabi- 

 tants of the large intestine, with the possible exception of the coccidia. 

 Mliller (1889) discovered it in the duodenum of one case at autopsy, an 

 observation w^hich was repeated by Moritz and Holzl (1892). Cohnheim 

 (1903, 1909) and Zabel (1901-1910) recorded what was probably G. intes- 

 tinalis in stomach contents in cases of carcinoma. Boyd (1921) in Canada 

 obtained large numbers of the flagellates by means of a duodenal tube 

 passed on a convalescent typhoid case. A similar observation has been 

 made by McGill (1922), Knighton (1922), Simon (1922), Silverman (1923), 

 and Libert and Lavier (1923). As the bile obtained by the operation 

 described as duodeno-biliary drainage contains large numbers of the 

 organisms, it is concluded that they have actually invaded the bile ducts 

 and gall bladder. This was confirmed by an observation of Smithies 

 (quoted by Knighton), wdio found the flagellates in the gall bladder at 

 surgical operation. Westphal and Georgi (1923) also record the discovery of 

 Giardia in a gall bladder opened at operation. The writer has seen G. i?ites- 

 tinalis in sections of the small intestine from fatal cases of typhus fever. 



The general shape of the flagellate and arrangement of the various 

 organs conform with the description given above (Figs. 291, 294). The 

 length of the body, not including the tail flagella, varies from 10 to 18 

 microns, though longer and shorter forms sometimes occur. The breadth, 

 which is a little more than half the length of the body, is subject to 

 greater variations than the length. Simon (1922) gives the following 

 measurements in microns for the flagellate: length 9-25 to 20-25 (average 

 13-7), breadth 5-0 to 10-25 (average 7-46). 



Encysted forms are very commonly seen in the stools of infected 

 individuals. It is only in diarrhoeic conditions that the free forms are 

 seen. The cysts are ovoid bodies varying in length from 8 to 14 microns 

 (Fig. 293). Simon (1921) gives for the length 8-0 to 14-0 (average 10-7) 

 microns, and for the breadth 6-0 to 10-0 (average 7-47) microns. In the 

 fresh condition the cysts are quite transparent. With careful observa- 

 tion it is usually possible to distinguish the nuclei, the central axonemes, 

 and some of the flagella. The nuclei are situated at the anterior end 

 of the cyst, and each of these may have divided to form a total of 

 four small spherical nuclei. In iodine solution or in stained films the 



