532 PROTOZOA 



surrounded by a slight space appears, which may or may not take a 

 deeper stain. In the larger forms there are more than one of these 

 granules. As many as eight have been seen. These may be arranged 

 more or less regularly about a central larger one, or scattered less 

 regularly throughout the substance of the body. 



We have also identified these bodies in smears of infected brains by 

 fixing the smear in methyl alcohol, and staining for twenty-four hours 

 by the Nocht-Romanowsky method as recommended by Ewing. The 

 bodies stain a robin's-egg blue or lilac, with dark-blue, more or less 

 regularly arranged granules or rings, one in the smaller bodies and 

 more in the larger, corresponding with the structure of the bodies seen 

 in sections. So far no similar bodies have been seen in control smears, 

 and it is evident that this might prove a reliable method for quick diag- 

 nosis; at least, in cases where these bodies are fairly numerous. It 

 seems to us possible that the bodies are protozoa and that they are 

 the cause of rabies. Their diagnostic value is certain. 



The bulk of the toxic material outside of the central nervous system 

 appears to be excreted in the saliva of the submaxillary gland, though 

 a certain small quantity may be excreted by the other salivary glands, 

 and also by the lacrymal glands, the pancreas, and the mammae of 

 rabid animals. The poison may also be found in the suprarenal bodies 

 and the peripheral nerves. 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 produced and its 

 severity have been found to be governed by three factors: (1) the 

 quantity of the rabic virus introduced; (2) the point of inoculation; (3) 

 the strength of the virus as determined by the kind of animal which 

 affords the cultivation ground for the growth of the hypothetical organ- 

 ism. It is a matter of common observation in hydrophobia of man 

 that slight wounds of the skin, of the limbs, and of the back are often 

 followed by the disease after an extremely long period of incubation; 

 while in lacerated wounds of the tip of the fingers, where small nerves 

 are numerous or where the muscles and nerve trunks are reached, or 

 in lacerated wounds of the face, where there is a similar abundance of 

 nerves, the period of incubation is usually much shorter and the disease 

 generally much more rapid. Experimental infection in animals is 

 produced with the greatest certainty when the material from the nerve 

 centre (the spinal cord or bulb) of an infected animal is injected into 



