138 
Entamoeba histolytica 
Penfold, Woodcock and Drew in 1916 announced that they had devised 
a method by which E. histolytica could be artificially induced to encyst. This 
was accomplished by the use of a solution of “Liquor pancreaticus” (Benger). 
From the cysts thus treated only one amoeba emerged, but whether it was 
uninucleate, binucleate, or quadrinucleate was not stated. 
These experiments I repeated with similar results except that the pro¬ 
portion of cysts which reacted to the treatment was small; further all the 
excysted amoebae were uninucleate. Further experiments have convinced 
me however that my results were pathological and due to the ferments dis¬ 
solving the thin cyst walls of amoebae which had just previously encysted. 
Dobell at this time also suggested to me that this was the explanation of the 
somewhat extraordinary result. A slight modification of the method adopted 
by Woodcock, Penfold and Drew has, however, proved more satisfactory. If 
a solution of “liquor pepticus” is first allowed to act on the cysts for a short 
time, followed by a similar solution of “liquor pancreaticus,” a very large 
proportion of the treated cysts react. Of the excysted amoebae some are 
uninucleate, as in the previous experiments, but the majority are quadri¬ 
nucleate, Plate VII, fig. 39. These forms I consider represent those which 
would emerge from the cyst under normal conditions, they move actively on 
the warm stage of the microscope, but though watched for five or six hours, 
I have not been able to observe them take any food or to determine definitely 
what is the next phase of their life cycle. 
That they are produced from E. histolytica cysts is evidenced by their 
general appearance, and by the fact that I have been able to stain them with 
methyl green during their emergence. 
The cysts, which did not react to treatment, were in the vast majority of 
cases binucleate. 
Although I have not seen the intermediate stages there is evidence that 
these quadrinucleate amoebae ultimately divide to form four small amoebulae, 
such as shown in Plate VII, fig. 40. 
Whether these amoebulae are gametes and conjugate, as in E. blattae, 
I cannot say at present. 
DEGENERATION IN E. HISTOLYTICA. 
As stated on p. 129, Schaudinn described a method of sporulation in 
E. histolytica , where the nucleus was converted into chromidia. Some of these 
chromidial granules passed to the periphery of the cytoplasm, which aggre¬ 
gated round them to form small buds, 3-7 /x in size. These buds became 
detached, secreted round themselves a thick wall, and became the spores or 
cysts of the parasite. 
Protozoa living in artificial culture are liable to undergo degeneration and 
E. histolytica has proved to be no exception to this rule: I have therefore 
made a full study of degeneration in culture forms and compared them with 
similar amoebae in the faeces of infected men. 
