4
THE RETINA.
We have found a further aid to the diagnosis of artificial rabies in the microscopical
examination of the retina. Negri bodies are demonstrated with difficulty in the nerve cells
o f
t h e b r a i n s o f a n i m a l s d y i n g f r o m f i x e d v i r u s i n f e c t i o n . I t i s n o t a l i t t l e c u r i o u s , t h e r e f o r e , t h a t
they should be so frequently present in the cells of the ganglionic layer of the retina in fixed virus.
infections as our investigations show.
The histological method adopted will be described later in the section devoted to Negri bodies-
in general; in this place the point is that Negri bodies of variable size, mostly .very small but
sufficiently conspicuous to be. recognised with a magnification of 500 diameters, have been seen
in. the great majority of the retinæ that we have examined of animals dying from fixed virus -
rabies, and that similar bodies have not been observed by us in the retinæ of animals dying from
other causes.
As this work was done purely for the purpose of ascertaining its value as a means of rapid
diagnosis a prolonged search for the bodies in numerous sections was never made; they were
found in. looking the length of not more than three adjacent sections well and good ; if not, the
preparation was thrown away and the result entered as negative.
TABLE No. 1 showing the results of the examination of the retina for Negri bodies
in rabid animals.
Animal i
Number
examined,
Point of entry of
virus.
Negri bodies found.
No bodies
found.
Numerous.
Scanty.
I
(Rabbits
...
•••
...
...1
24
Subdural ...
..
14
6
4
IGuinea-pigs ...
...
...
... I
32
Do....
...
23
7
2
Cats ...
...
.• •
•••
••• 1
1
Do.
...
...
1
•••
•.•
Goats ...
...
...
,..
•••
2
Do,
.••
•••
. • .
2
•••
Do
-• •
2
1
Guinea-pigs ...
...
...
...
4
Subcutaneous
..
...
1
3
(Rabbits
...
...
•••
•••
2
Subdural -••
...
...
2
.• •
I Guinea pigs ...
...
...
...
...
4
I Cats ...
•••
...
•••
1
Do.
...
...
•••
•••
1
1
.;...
' Dogs ...
...
'
...
.•.
...
2
1
1
Mus Rattus ...
..
.••
•••
4
Subcutaneous
...
•••
4
Nesokia Indica
...
.••
•••
1
Do.
•••
•• •
•••
1
Rabbits
...
...
•••
1
Sciatic
..•
•••
•••
.•.
1
(Dogs
...
...
...
1
Natural
...
..
..•
...
1
The most striking things about Table 1 are, firstly, the number of negative findings in animals
infected by the subcutaneous route and, secondly, the smaller proportion of positive findings.
with street virus as compared with fixed virus,. although simultaneous preparations of the hippo-
campus major showed abundant Negri bodies in all of these street virus infections.
The numbers are evidently too small to allow any definite conclusions to be drawn ; but the
notion that a scrutiny of the eyes of dogs which have bitten human beings might come to replace
that of their brains, which presented itself to us at an early stage, looks as if it will have to be
abandoned., since no bodies could be found in the retina of the only two naturally infected dogs
we have so far obtained.
It is stated by Frösch (8) that the retina is not infective, but we have not made any experi-
ments to confirm this. Frösch, however, omits to mention which kind of virus he is referring to.
THE STOMACH.
Another exceedingly common but not entirely specific macroscopic lesion in guinea-pigs, rats
and rabbits dying from rabies is the occurrence of haemorrhages in the stomach. These may be
only two or three in number and about 1 or 2 mm. in diameter, when they are usually found on
the posterior surface of the cardiac end of the stomach. At other times 20 or more similarly small
discrete haemorrhages are seen chiefly at the cardiac end. More rarely large irregular hæmorrha-
gic patches are seen. Microscopic sections show that there is necrosis of the whole thickness of
the mucous membrane as well as exudation of blood at these points.