2
The rectal temperature of normal rabbits varies between 101° F and 102° F. It may rise to
103° F or sink to 995° F without anything being wrong with the animals as far as one is able
to judge.
Chart 1 shows the mean daily rectal temperature taken morning and evening *of 24 rabbits
inoculated subdurally with fixed virus. It will be noticed that the first sign of a rise in the
temperature occurs at the end of the 4th day, that the rise is more pronounced on the fifth day and
that the highest point is reached on the 6th day.
Thereafter the fall is rapid till death occurs.
Among these 24 rabbits the highest temperature recorded was one of 105° F on the evening
of the sixth day. Some of the animals had a temperature of 103 . 6° F as late as the evening of the
ninth day, while others fell to between 94° F and 97° F as early as the evening of the seventh
day. In one the temperature remained betwen 90° F and 91° F for 48 hours before death, but it
did not often keep below 94° F for inure than 12 hours.
The temperature of the air was observed. to have a considerable influence on that of the
rabbits, since it was only when it fell to an average of 60° F that the very low subnormal figures
were recorded.
Chart 2 shows the mean daily variations in weight of 12 rabbits inoculated subdurally with
fixed virus. Little change is seen until the seventh day, when a sharp fall occurs which is
continued daily until the end.
The interpretation of the temperature curve (chart 1) is not quite simple as regards its ascent.
The fever may be due to one of two causes :-
(a) the presence of toxic substances in the circulation which are either excreted by the
organism of rabies itself or are liberated from the nerve cells undergoing disintegration in
consequence of its multiplication and growth.
(b) direct interference with the centres which control the heat of the body by the growth
of the parasite in their neighbourhood. Most writers on rabies with the exception of Babes have
expressed the opinion that there is no evidence of the formation of any specific toxin by the
causative agent of rabies. To this question we shall return later (section 7). Fcr the present it
suffices that the fever is explicable on one or both of the following, assumptions, namely, the
presence of the products of nerve tissue disintegration in the system and the direct irritation of
the heat centres. The explanation of the fall is more certain. It must be imagined that rabies
is due to the multiplication of what is probably a purely intracellular parasite of a nature not yet
determined in the central nervous system. Whether toxic matters are excreted by the parasite
or not is of little import, for if they are the quantity must be small or the quality of slight
virulence. These parasites have their seat of election in the central nervous system and the
symptoms which are manifested in the course of the disease depend on the implication of
different nerve centres. With suddural inoculation of fixed virus there are only slight variations
in the symptoms, as the virus travels by much the same route on each occasion, but the variations
are great when the virus is inoculated subcutaneously, as happens when one rabid dog bites
another, for then the organism can reach the nerve centres by many routes ; and though practically
the whole nervous system is infective at the time of death the incidence of the disease has been
more severe on some parts than on others.
It is evident from the great fall of temperature that the heat maintaining mechanism is
specially interfered with.
The loss of heat does not seem to be due to dilatation of the cutaneous vessels, for great
difficulty is experienced in obtaining even a single drop of blood for examination from the
posterior auricular vein. It may be conjuctured that the primary fever is in some way connected
with irritation of the cortex and other parts of the brain by the presence in it of the organism
of rabies, a condition well known to but unexplained by physiologists, and that the subsequent
low temperature is caused by the partial destruction of the previously irritated governing centres.
The interpretation of the weight curve (chart 2) is straight forward. On the seventh day,
when the temperature is at its highest and the earliest manifestations of muscular weakness are
usually observed, the appetite begins to fail or more probably there is some interference with the
mechanism of deglutition, and the animal finds itself unable to swallow with ease. This, combined
with the rapid increase of general motor paralysis, keeps the animal from food, and the weight in
consequence steadily decreases.
The muscles of deglutition are not always affected as early as the seventh day, for an animal
will occasionally masticate and swallow quite well long after paralysis of the front and hind
quarters is marked.
THE URINE.
Having noticed in the course of the dissection of passage rabbits that the bladder was
frequently, greatly distended, sometimes containing from 50 cc to 60 cc, we systematically examined
the urine in a number of passage rabbits and found that albumen was usually, though not
* By Hospital Assistant S. Ramasamy Aiyar.