MASTIGOPHORA 1075 



provided with a sucking disk anteriorly. There are eight pairs of 

 fiagella, the two posterior ones being continuations of longitudinal 

 axostyles. The nucleus is first dumb-bell shaped and later divided 

 into two separate nuclei. Cysts are found, and according to Scliau- 

 dinn conjugation occurs in them with the development of four 

 nuclei. The young parasites attach themselves to the surface of 

 epithelial cells of the small intestine by the sucking disk, but even 

 when present in large numbers do not produce any characteristic 

 symptoms. Giardia infestation is quite common in children in the 

 United States, and not uncommon in adults. Maxcy* found 20 per 



FIG. 133. LAMBLIA INTESTINALIS. Cyst formation. (After Doflein, " Lehrbuch der 



Protozoenkunde . " ) 



cent of children infested and Kofoid found 6 per cent of young 

 healthy soldiers harboring the parasite. The same or like parasites 

 are present in mice, rats, dogs, cats, and sheep. Transmission is 

 by contact, as in trichomonad infections. 



ORDER II PROTOMONADINA 



The Protomonadina, another order of the Flagellata, have less than 

 three flagella, and are divided into the Cercomonadidce, Bodonidce and 

 the Trypanosomidce. 



GENUS 1. Cercomonadidae Cercomonas hominis (Davaine, 

 1854). As originally described, this organism has a pear-shaped body, 



* Maxcy, Kenneth F., Johns Hopkins Hospital Bull., 1921, 32, 166. 



