ROBERT HEGNER 673 



of the fecal material examined is not fresh and the results of examinations are based 

 largely on the finding of cysts, whereas the trophozoites of T. hominis are not so easy 

 to find. Thus, Boeck and Stiles (1923) noted only 0.07 per cent of this species in their 

 large survey of eight thousand and twenty-nine individuals in the United States. In 

 this survey fecal specimens from twenty-two states were examined many of which 

 were several days old when received. Paulson and Andrews (1927) report an inci- 

 dence of 4.3 per cent in two hundred and ten persons in Baltimore, from examina- 

 tions of fresh stools. Hegner (1925) found 20.6 per cent of infection among natives 

 of Tropical America and Hill (1926) obtained similar results in Porto Rico. 



The best method of determining the presence of Trichomonas hominis, as first 

 pointed out by Hegner and Becker (1922), is to inoculate cultures with a small sample 

 of fecal material. The best medium seems to be the serum-saline-citrate mixture. 

 This consists of a stock solution containing 0.07 per cent sodium chloride, and i.o per 

 cent sodium citrate. The medium is made up by adding to 100 cc. of this solution 

 500 mg. of Loefiler's dehydrated blood serum. Cultures should be incubated at 

 37° C. and examined at the end of forty-eight hours. As in the case of the amebae 

 that are transmitted by fecal contamination, insanitary conditions, flies, and perhaps 

 other animals are largely responsible for the transmission of this flagellate. 



The ingested trophozoites of Trichomonas hominis are carried through the stomach 

 and small intestine and set up an infection in the large intestine of susceptible hosts. 

 Here they find conditions favorable for growth and reproduction. In the case of rats, 

 which are infected with a species of trichomonad, T. muris, similar to the human 

 intestinal form, Hegner (1923) has shown that a carnivorous diet apparently changes 

 the character of the contents of the large intestine so as to react favorably against the 

 parasite. It is suggested that the unfavorable conditions produced are due to a change 

 in the bacterial flora from acidophilous to putrefactive types. A meat diet suggested 

 by the writer (Hegner, 1924) for the treatment of flagellate diarrhea has met with 

 success in a number of cases. 



Whether or not the trichomonads that live in the human intestine are pathogenic 

 is a problem still unsolved. Frequently enormous numbers are found in cases of so- 

 called "flagellate diarrhea" where no other cause for the diarrheic condition could be 

 determined. The type of trichomonad with five anterior flagella, frequently called 

 Pentatrichomonas, is most frequently associated with diarrheic conditions. This form 

 ingests red blood cells with avidity but has not yet been found guilty of tissue in- 

 vasion. If trichomonads are not responsible for flagellate diarrhea, they are present 

 in such large numbers when this condition exists, probably because they find the 

 intestinal content at this time particularly favorable for growth and reproduction. 



4. Giardia lamblia. — A cyst stage occurs in the life-cycle of Giardia lamblia, and 

 hence this species is no doubt transmitted by the same agencies as is Endamoeba his- 

 tolytica (see p. 667). The cysts must gain access to the food or drink and are thus 

 ingested by susceptible human beings. Cysts are apparently quite resistant to factors 

 in the environment outside of the body and remain viable for many days. The inci- 

 dence of infection with Giardia lamblia in the general population appears to be about 

 10 per cent. 



Giardia lamblia is the only intestinal flagellate that lives in the small intestine of 



