220 THE PROTOZOA 



A method for bringing out the nuclear features is as follows: take a loopful of 

 2% acetic acid and a loopful of 2% formalin. Tinge the mixture to a rose color 

 with neutral red and then stir in a little saturated aqueous solution methyl green, 

 using a tooth pick which has been dipped into the methyl green. 



In staining with iron haematoxylin or better with phosphotungstic haematoxylin 

 proper fixation is very important. Fix in 100 parts of sat. aq. sol. bichloride to 

 which is added 50 c.c. absolute alcohol and 5 drops glacial acetic acid. The stain 

 should be poured on the moist smear of faeces. The fixative should be heated to 

 60 C. and should only act for 10 to 20 seconds. Then place in cold sublimate 

 alcohol for 10 minutes wash in 70% alcohol colored to a rich port wine color with 

 iodine, then in 70% alcohol, then in water and then stain as preferred. Some like 

 a carmine stain. 



E. coli varies greatly in size (8 to 40^). There is no well-marked distinction 

 between a granular interior and a more compact, hyaline exterior. The nucleus is 

 centrally situated, is distinct, and on staining with Wright's stain shows the chro- 

 matin coloration. The nucleus is rich in chromatin and with iron haematoxylin it 

 shows four chromatin aggregations lining the nuclear membrane. It is sluggishly 

 motile and is of a grayish-white color. When stained it does not show a distinction 

 between endoplasm and ectosarc. The infecting stage is an encysted form with 

 eight nuclei or spores. 



Entamceba histolytica (Amoeba dysenteriae). This is considered 

 the pathogenic amoeba. Schaudinn considered that it was by the 

 possession of its tough, tenacious glassy, and highly refractile ectoplasm 

 that it was able to bore its way into the submucosa of the large intestine 

 and bring about those gelatinous-like necroses, which, by undermining, 

 eventually result in dysenteric ulcerations. 



It was also thought to be the species found in tropical liver abscess. 

 As described by Schaudinn, it has a marked differentiation between the 

 glassy ectoplasm and the granular endoplasm. The nucleus is indis- 

 tinct, eccentric, or even peripherally situated, and stains feebly. 



The movement is more active and the color more greenish-yellow than E. coli. 

 Craig notes the characteristic staining of the E. histolytica, this being a dark blue 

 ectoplasm encircling a lighter blue endoplasm. In dividing, there is a process of 

 budding. These little spore-like bodies form at the periphery of the encysted amoeba 

 and are the infecting stage. Faeces should be examined as soon as possible after 

 the stool is passed in order that one may have the best opportunity to observe 

 movement. A particle of mucus pressed down with a cover-glass makes a satis- 

 factory preparation. If necessary to dilute, use blood-warm salt solution not 

 plain water. 



Amoebae were first described by Lambl in 1859. Found by Loesch in dysenteric 

 stools in 1875. Councilman and Lafleur in 1891 separated amoebae into pathogenic 

 and nonpathogenic strains. 



Kartutis produced dysentery in cats by introducing dysenteric stools into the 

 rectum. Kruse and Pasquale produced dysentery with liver abscess pus which 



