OF THE ALniENTARY TRACT 187 



HABITAT AND EFFECTS 



The home of Giardia intestmalis is the upper small 

 intestine, apparently mainly the duodenum, instead 

 of the caecum as with Trichomonas and Chiloviastix. 

 Here the organism finds the environment and mate- 

 rials suited to its well being and multiplication. That 

 its needs are radically different from those of other 

 flagellates is given evidence by its structure, the 

 absence of bacteria from its body, and its failure to 

 survive in media which will grow others well. As 

 it passes down the intestine it becomes encysted and 

 prepares for transference to a new host in mutiplied 

 form. 



It is believed that the oral sucker is the means of 

 maintaining its position and it has been seen at- 

 tached by this apparatus to the epithelial surface 

 of the mucosa. It has not been ascertained that it 

 damages these cells or excites any reaction on the 

 part of the mucosa, although some believe that it 

 irritates the epithelium and stimulates mucus produc- 

 tion. 



The term '^giardiasis" has, at the present time, 

 no definite meaning beyond the presence of the para- 

 site in the intestine. In children Giardia has been 

 suspected of an etiologic role in persistent diarrhoea, 

 with clear or yellowish mucus, in which are seen large 

 numbers of the active form of the organism, con- 

 spicuous in the stool. 



Hill and Hill (1927) in a survey of children of pre- 



