RABIES 399 
as the ganglion is removed it is placed in Flemming’s fluid or in a standard aqueous 
solution of mercuric chloride for a few hours, washed in water, carried through the 
alcohols and sectioned by the paraffin method. With this method of fixation it is 
almost imperative that the sections be stained with iron or Delafield’s hematoxylin, of 
which we have found the latter the most convenient. Alcohol, either 95 per cent. or 
absolute, may be used as a fixer, in which case other staining methods may be used. 
However, the fixation by this method is not as good, but it admits of a trifle more haste. 
Normally this ganglion is composed of a fibrous capsule from which 
a supporting fibrous tissue extends into the interior, holding in its 
meshes the nerve cells, each of which is enclosed in an endothelial 
capsule. The changes characteristic of rabies consist in the atrophy, 
the invasion and the destruction of the ganglion cell as a result of new 
formed cells, evidently from the endothelial capsule. These cells 
appear first between the nerve cell and its capsule. These changes 
are quite uniform through the entire ganglion and in advanced cases 
of the disease nearly all of the nerve cells are oftentimes destroyed. 
The fact must be kept in mind that this is a method for rapid diag- 
nosis in case the animal dies and not a means for an early diagnosis. 
This method is not trustworthy if the animal was killed in the early 
stages of the disease as the changes do not appear until later in its 
course. 
Diagnosis by animal ineculation. The method experience has shown 
to be the best is the subdural inoculation of rabbits or guinea-pigs 
with a suspension of the brain or spinal cord of the suspected animal. 
The subdural inoculation with the brain tissue of rabid animals was 
first demonstrated by Pasteur to be more reliable and more rapid in 
its results than the subcutaneous injection. 
The procedure is simple. The brain of the suspected animal is removed with aseptic 
precautions as soon as possible after death. A small piece of the brain or spinal cord 
is placed in a sterile mortar and thoroughly ground with a few cubic centimeters of 
sterile water or Louillon. This forms the suspension to be injected. 
The hands of the operator and all instruments are carefully disinfected. The rabbit 
is etherized, the hair clipped from the head between the eyes and ears, and the skin 
thoroughly washed and disinfected. A longitudinal incision is then made, the skin and 
subcutaneous tissue held back by means of a speculum, a crucial incision is made in the 
periosteum on one side of the median line, to avoid hemorrhage from the longitudinal 
sinus, and the four parts of the periosteum reflected or pushed back. By the aid of a 
trephine a small button of bone is easily removed leaving the dura mater exposed. With 
a hypodermic syringe a drop or more of the rabid brain suspension is injected beneath 
the dura, the periosteum is replaced, the skin carefully sutured and disinfected and the 
rabbit returned to its cage. As soon as the influence of the anesthetic* has passed off 
*Ether should be used in preference to chloroform for rabbits, as the latter frequently 
causes death, while the former can be administered with comparative safety. 
