69 2 Dysentery 



testinal evacuations of dysentery the protoplasm commonly 

 contains many red blood-corpuscles, upon which the organ- 

 ism seems to feed. 



Staining. When stained with polychrome methylene-blue 

 the ectoplasm stains more deeply than the endoplasm. The 

 nucleus contains relatively little chromatin. 



Reproduction. Multiplication takes place by binary divis- 

 ion after karyokinesis and by encystment and sporulation. 

 The sporulation is quite different from that seen in Enta- 

 moeba coli, and only takes place when conditions are unfavor- 

 able to continued division. It is accomplished by a peculiar 

 nuclear budding, by which chromatin granules or chronidia 

 are pushed out from the nucleus toward the ectoplasm, where 

 they develop into new nuclei, about which the cytoplasm 

 collects until a distinct bud is formed and cast off as a small 

 but distinct new organism a spore or bud. These when 

 separated are round or oval, measure 3 to 6 p in diameter, 

 and are surrounded by a yellowish envelope, which resists 

 drying and the penetration of stains and chemicals. 



Craig gives (see page 693) a tabulation of the differential 

 features of Bntamoeba coli, Bntamoeba hystolytica, and 

 Entamoeba tetragena. 



3. Entamceba Tetragena. This organism resembles En- 

 tamoeba hystolytica more than Amoeba coli, but differs from 

 it in the mode of reproduction. The sporocysts contain but 

 four instead of eight spores. 



Isolation and Cultivation. Many experimenters have made 

 more or less successful attempts to cultivate ameba. Mus- 

 grave and Clegg,* whose interesting paper the student will 

 do well to read, and in which he will find a complete review of 

 all antecedent work, were able to cultivate a considerable 

 variety of amebas upon agar-agar made of : 



Agar 20. 



Sodium chlorid 0.3-0.5 



Extract of beef 0.3-0.5 



Water 1000.0 



Prepare as ordinary culture agar, and render i per cent, 

 alkaline to phenolphthalein. The finished medium is poured 

 into Petri dishes. To obtain the greatest number of most 

 active amebas the patient should be given a dose of a saline 

 purgative, and the fluid evacuation resulting from its action 

 employed for inoculating the media. The cultures are, natu- 



* "Department of the Interior, Bureau of Government Laboratories, 

 Biological Laboratory," Manila, Oct., 1904, No. 8. 



