268 
Negri bodies 
These small iron staining granules are regarded by some as being 
the actual parasites, round which the cytoplasm has reacted to produce 
the large Negri body. It is the cyst-like membrane which enshrouds 
the individual granules like a mantle that has led to their being named 
Chlamydozoa. The granules are not found in every case. In fact we 
observed them only io the dog and never in the guinea-pig or rabbit. 
Nor have we seen any evidence of a ‘ budding phenomenon ’ or dumb¬ 
bell-shaped division figures. These facts go in our opinion to support 
the view that the parasite of rabies has not yet been microscopically 
demonstrated. There is however no reason from our observations to 
negative the idea of the presence of a parasite as a cause of the 
phenomenon of Negri body formation. We next come to consider the 
significance of the yellow masses found in man, i.e. in the brains of 
subjects dyiog from rabies, and also seen to some extent in lower 
animals {e.g. mule and horse). These masses are apparently very 
constantly present in rabies, but they are not absolutely diagnostic. 
Can we consider them, on our hypothesis, to be in any way composed of 
substances derived from the nucleolus of the nerve cell ? By Mann’s 
stain the nerve cell containing these masses shows a nucleolus which 
exhibits a yellow centre with a red stained zone around it (PL XI, 
fig. 2), that is to say the centre of the nucleolus stains (or does not 
take a stain) in the same manner as the yellow masses in the cytoplasm. 
We saw that in certain ova (Text-figs. 1, 2; oocyte of Antedon bifida) 
nucleolar discharges occur and give rise by aggregation to the so-called 
yolk nucleusL These yellow masses, found in human brains, might 
easily be similar aggregations of nucleolar discharge set up by the 
action of a virus (like rabies virus) upon the nerve cell. From these 
researches and observations we are led to the following conclusioms. 
Conclusions. 
(i) Negri bodies are not parasitic in nature, but are derived from 
extruded particles of nucleolar matter. 
(ii) The extrusion is the result of katabolic changes in the nerve 
cells caused by the action of the rabies virus. Such an extrusion is also 
brought about by normal stimuli as is shown by the work of many 
observers. 
1 It may be advisable to avoid confusion by saying that the term here has no 
connection with the nucleus of a cell. 
