I"\I< ITY OF OXYGEN* FOR PROTOZOA. 461 



When cocki - are confined in oxygen at 3.5 atmosphen 



they are able to li\ e approximately 90 hours, which is 26 times as 



Ion:; as their ciliati- and 135 times as long as their flagellate proto- 



thi- pn ->ure. Here, again, as in termites, it i> evident 



that tl tion which removes the protozoa of cockroaches 



ly <Ioe> little, if any. harm to the cockroaches themselve-. 



They, unlike termites, live normally (indefinitely) after their pro- 



tozoa ha\e 1- -noved. Oxygen, then, at 3.5 atmosphere- i> 



ic for the flagellates and 26 times as toxic for the ciliates 



li\ ii ' hes as it is for the insects themseh 



3. Earthworms. 



Many earthuorms, harboring a fa.ny large number of ciliate- 

 if the -^eiiii- I/KpIitflphyra. were oxygenated at 3.5 atmosphere-, 

 but tin- minimum time required to kill their protozoa was not 

 determined, h is more than six and less than twenty hours. 



4. Frogs. 



Alter all protozoa had been removed from three invertebrai 

 ii -eemed h iiJiK desirable next to oxygenate a cold-blooded \erte- 

 br.itr h. n!. many protozoa. For this work the frog (Rumi 



{>ij --cted. 



MCI-I frogs harbor an abundant protozoan fauna; two aliate-, 

 totherus, and four flagellates, Trichonwnas (Tri- 

 tri< /ni. <i,i\ in the opinion of some investigators), Chilonnistix, 

 Hexamitus, and Polymastix. arc usually present in a fairly la 

 number >\ h.-i-; in fact, all are sometimes present in the same 

 h<. -t. T\\<. hundred frogs were procured and just before bein:>; 

 u-ed in experiments each indi\'idual was examined in order to 

 ascertain \\lut protozoa were present. This examination \\a- 

 made 1>\ attaehing a No. 7 hard rubber catheter, cut off at the 

 in>ei tii.n end [ four inches in length, to a 5 cc. Luer syringe: \<\ 

 in^ei tin.u the eatheter into the rectum it was possible to draw out 

 all or any amount of the rectal contents, which, \\hen examined 

 under the mi. roscope, revealed immediately \\ hat protozoa ea< h 

 frog harbored. M ourse, the number of protozoa present was 

 also aM'ertained at the -a me time. 



\\ hen 1'rou- \\eit 0x5 ^enated at 3.5 atmospheres, it was found 

 that some of their inte>tinal protozoa were killed more quickly 



