Volume XT 
FEBRUARY, 1919 
No. 2 
OBSERVATIONS ON ENTAMOEBA HISTOLYTICA. 
By D. WARD CUTLER, M.A. (Cantab.), 
Assistant Lecturer in Zoology , Victoria University, Manchester. 
(With Plate VII and 1 Text-figure.) 
CONTENTS 
1 . 
Introduction 
PAGE 
127 
2. 
Methods ....... 
128 
3. 
Literature ....... 
129 
4. 
Effects of Various Substances on Amoebae in 
Culture . 
130 
5. 
Appearance of the Living Amoeba 
131 
6 . 
Pseudopodia. 
132 
7. 
Food Ingestion and Digestion 
132 
8. 
Morphology and Nuclear Division 
133 
9. 
Cyst Formation ...... 
135 
10. 
Chromatoid Bodies . ... . 
137 
11. 
Further Development of the Cyst . 
137 
12. 
Degeneration in E. histolytica 
138 
13. 
Discussion ....... 
141 
14. 
Summary ....... 
143 
15. 
References. 
144 
16. 
Description of Plate VII .... 
145 
INTRODUCTION. 
A very large number of publications dealing with Entamoeba histolytica have 
appeared during the past few years, but we still lack any detailed account of 
the various changes which this organism undergoes during its life history. 
The elucidation of the meaning of these changes of form has been one of 
the objects of my research during the past two years. For many months I 
have been employed on the routine examination of the faeces of patients who 
were either suffering from amoebic dysentery or else were suspected of being 
carriers of E. histolytica. It was my practice during these examinations to 
make stained preparations of any amoebae found in the stools, and by this 
means I have been able to accumulate a large number of preparations for 
careful study. 
Early in 1917 I devised a method (Cutler, 1918) by which the amoebae 
could be kept in artificial culture for many months. Six cultures were obtained 
and inoculated into cats, all of which died of typical amoebic dysentery. 
These cultures and the material from the infected cats have enabled me to 
make a fairly complete study of the forms assumed by E. histolytica , and also 
Parasitology xi 9 
