660 APPENDIX. 
Etiology and Pathogenesis. The etiology and patho- 
genesis of rabies are still but imperfectly understood. 
The poison, whatever may be its nature, is usually con- 
tained in the saliva; and as early as the beginning of 
this century experimental rabies was produced in the 
dog by inoculation with the saliva of a hydrophobic 
patient. The bulk of the toxic material appears to be 
excreted in the saliva of the parotid gland, though a 
certain small quantity may be excreted by the other 
salivary glands, and also by the lachrymal glands, the 
pancreas, and the mamme of rabid animals. The 
poison may also be found in the suprarenal bodies and 
in the fluid and substance of the cerebro-spinal nervous 
system, especially the medulla oblongata; it is found 
also in the peripheral nerves, though in much smaller 
quantity than in the central nervous system. It has not 
been found in the blood, the urine or the aqueous humor 
of the eye; it has been reported to have been found in 
the foetus. 
That the disease is due to some form of organism 
which has the power of multiplying in the tissues and 
of producing a toxic substance, which appears to act 
specifically upon the central nervous system, cannot 
be doubted. As in other specific infectious diseases, 
the virus is transmitted directly from animal to animal 
through the medium of some fluid or secretion; it is 
now very generally recognized that the disease cannot 
arise anew, as was at one time assumed. In rabies, 
again, as in other infectious diseases, there is a period of 
incubation during which the poison appears to increase 
in quantity. 
The certainty with which the disease may be pro- 
duced and its severity have been found to be deter- 
