140 
Entamoeba histolytica 
Similarly it can be shown that excess or deficiency of food supply does 
not produce degeneration, for cultures apparently identical, as regards 
available food, will vary considerably. It must be recognised, however, that 
cultures containing many forms of bacteria, as my cultures do, are not living 
under the same conditions; and the various bacterial products may be very 
different both quantitatively and qualitatively in the various cultures. 
Probably these substances have a decided influence in causing degeneration. 
Dobell, from studies on E. rana-rum , concluded that temperature, together 
with an unknown factor preventing the extrusion of chromidia, is the cause 
of degeneration. 
This suggestion seems applicable to E. histolytica , for the incubation at a 
lower temperature than the normal would cause nuclear overgrowth, which 
for some reason or other (bacterial products might here come into play) is 
unable to be compensated by the extrusion of the excess chromatin into the 
cytoplasm. Possibly the irregular nuclear divisions are an expression of this 
need on the part of the organism. 
Further it is significant that in cat infections, where cyst formation with 
chromatin extrusion is rare, degenerate amoebae are common. Such amoebae 
often fuse together. Plate VII, fig. 54 was drawn from a preparation made from 
the faeces of a patient, while fig. 55 represents fused amoebae in the lumen 
of a large intestinal tubule of an infected cat. The nuclei exhibit degeneration 
changes. 
Degeneration recorded by other Observers. 
Hartmann dealing with E. tetragena distinguished two types of degenera¬ 
tion forms. In the first the nucleus was swollen with large clumps of chromatin, 
while in the second the nuclear membrane disappeared. I think from my 
work that it is evident that this second type is the continuation of the process 
begun in the first type. Darling considers that the buds so often seen in 
E. histolytica are due to degeneration, a view in which I thoroughly concur. 
Bartlett in a recent communication has described cells, often associated 
with E. histolytica, which he termed retractile cells. His figures suggest that 
they are degenerate amoebae. 
The active movement, which these bodies exhibit, is no bar to this view. 
The following is the description which Bartlett gives of the retractile 
cells “ In unstained films they are extremely well-defined rounded cells, which 
are more refractile than the body cells, but less retractile than the vegetative 
entamoebae; they are greyish rather than greenish in colour. They vary in 
size from that of a neutrophil leucocyte to a large phagocytic endothelial 
cell. The nuclei may be single and of small size, or may be multiple. When 
multiple they may be two, four or more in number, and may be equal or 
unequal in size. The nuclei show characteristic crescentic thickenings on 
their margins.” 
As will have been noted this description, especially as regards the nucleus. 
