C. Dobell and M. W. Jepps 
351 
Mathis, C. and Mercier, L. (1917 a). Existe-t-il des kystes a plus de qiiatre noyaux 
chez Entamoeba dysenteriae? Bull. Soc. Pathol. Exot. x. 165. 
- (1917 b). La schizogonie chez les entamibes intestinales de I’homme. Ibid. 
311. 
Wenyon, C. M. and O’Connor, F. W. (1917). An inquiry into some problems 
affecting the spread and incidence of intestmal protozoal infections, etc. Part II. 
Journ. Royal Army Med. Corps, xxvni. 151. 
Woodcock, H. M. (1917). Protozoological experiences during the summer and 
autumn of 1916. Ibid. xxix. 290. 
DESCRIPTION OF PLATE VI. 
The figures in this plate have been drawn to show at a glance the differences in the 
dimensions of the cysts of E. histolytica in the four cases (H. 8, H. 7, E. 42, B. 1) described 
in the text. They sliow in parallel columns ten cysts from each of these cases. The cysts 
were not selected, but represent in each case ten consecutive cysts in the order in which 
they appeared in examining the preparations at random under the microscope. The pre¬ 
parations were aU fixed, stained, and mounted in the manner described in the text. The 
drawings show merely the outlines of the cysts, tlieir nuclei, and chromatoid bodies (black) 
when present. The outlines were drawn as accurately as possible with the camera lucida, 
at a magnification of 2500 diameters (Zeiss 2 mm. apochromat, N.A. = 1-40, compensating 
ocular 18), and have been reduced to the size shown in the proce.ss of reproduction. The 
figures illustrate not only the differences in the dimensions of the cysts in the four races of 
E. histolytica described, but also the kind of asymmetry observable in the outlines of the 
cysts themselves, which renders a perfectly accurate determination of their diameters 
extremely difficult. 
The remaining figures are outhnes of fixed and stained amoebae, drawn in the same way 
to the same scale, to illustrate the size of the unencysted organisms as compared with their 
cysts. Fig. E. h. (1) shows two individuals of the tissue-inhabiting form (“histolytica” 
form) of E. histolytica, from a case of acute dysentery. The amoebae belong to a race 
producing cysts similar in size to those of Case E 42. Fig. E. h. (2) shows two small pre- 
cystic amoebae (“minv.ta” forms) from a subacute infection, and belonging also to a race 
of E. histolytica havmg cysts of similar size. Fig. E. h. (3) shows a pair of precystic amoebae 
(“mimita” forms) belonging to a race with cysts similar in size to those of Case H. 8. 
(The black masses in Fig. E. h. (1) are the remains of ingested red blood-corpuscles.) The 
amoebae were not specially selected individuals, but were taken at random from prepara¬ 
tions in which large numbers were present. 
