SARCODINA 731 



is rarely any separation of ectoplasm and endoplasm, but the nucleus 

 is always visible. The cytoplasm is granular and has a coarse honey- 

 combed' appearance. The nucleus shows a distinct, though delicate, 

 limiting membrane, on the inner surface of which are few or many 

 chromatin dots. In the center is a small karyosome, which may show 

 a central body or centriole. The outer zone of the nucleus has a honey- 

 comb structure, in which are imbedded granules of chromatin. 



Multiplication in the vegetative stage is by division into two daugh- 

 ter cells, and dividing cells are common after the disease has existed 

 for some time and the amebae are preparing to encyst. At such time's, 

 due probably to rapid division, the amebae are small and the nucleus 

 shows various stages of a simple mitosis ; at the poles of the delicate 

 spindle may be seen the two new centrioles ; this may be detected even 

 in unstained specimens. 



Degenerative Forms. These are extremely common in stale stools, 

 in cases during convalescence, or under active treatment, and also in 

 experimental dysentery in the cat, and they have led to much con- 

 fusion in the past. The nucleus breaks up into fragments and chro- 

 matin masses are extruded into the cytoplasm in irregular forms, and 

 parts of the cells are apparently budded off. At one time the budding 

 process was looked upon as normal by Schaudinn and his followers, 

 but there is now little doubt ^iat both spores and buds are degenera- 

 tive changes and that the animal multiplies only by binary fission in 

 the vegetative forms or by the development of four nuclei in the cysts. 



Cyst Formation. The cyst of Endameba histolytica was first de- 

 scribed by Viereck as Endameba tetragena, and for a time was believed 

 to be a new species. In fact, Hartmann described a vegetative stage 

 of Endameba tetragena as Endameba africana, afterwards accepting 

 the name i l tetragena, ' ' but it is now apparent that tetragena is merely 

 the end, or cyst stage, of Endameba histolytica, which had formerly 

 been overlooked. Cysts are not easily found in all cases, and it is 

 possible that when treatment is vigorous they never develop. They 

 are, without doubt, the form in which the parasite leaves the body to 

 infect new victims ; because of their heavy cyst wall they are quite re- 

 sistant to drying and other harmful influences. It is also possible that 

 they may be retained in the wall of the colon and so be the starting- 

 point of the relapse, which is so characteristic a feature of amebic 

 dysentery. The protoplasm of the cyst and the precystic stage is 

 granular, but shows no vacuoles nor cell inclusions. The nucleus un- 

 dergoes division by mitosis first into two, and then four small ring-like 



