IDO ANNUAL ttErORT OF THE Off. Doc. 



pi'oduce the disease with material In which the bodies are demon- 

 strated. They liave been found in tb(! l;iij;or nerve cells of the brain, 

 in the cerebellum, hippocampus major, medulla chlongata and 

 cerebral cortex. They have never been demcmstrated in the nerve 

 trunks, but they have been seen in the nerve cells of both the plexi- 

 form ganglicm and the ganglion closely associated with it — the sym- 

 pathetic ganglion. Attempts to demonstrate Negri bodies in the 

 saliva or salivary glands or the milk or the mammary glands, lachry- 

 mal secretion or lachrymal gland, and pancreatic secretion or pan- 

 creas, has never been successful, nor have Negri bodies been found 

 in the blood or any of the tissues of the body excepting those named 

 of the nervous system. It will be extremely difficult to satisfactorily 

 explain, when Negri bodies are accepted as protozoa and the cause 

 of rabies, why it is that these bodies cannot be demonstrated in the 

 saliva or salivary glands or other body secretions or glands which are 

 known to contain the virus, but some light may be thrown upon this 

 puzzling fact when it is remembered that the life cycle of many of 

 the known rhizapods or sporozoa is extremely complicated and spore 

 forms or sporozoits exceedingly small are formed some which may be 

 of the size, out of the zone of vision. It is therefore reasonable to 

 conclude that similar small sporozoit formation may be a part of the 

 life cycle of the Negri body protozoon, and that it is the small sporo- 

 zoits in the saliva and other secretions which have as jet not been 

 demonstrated. Negri bodies were first demonstrated in sections of 

 the brain tissue and many different stains are in use. They are 

 readily demonstrated in sections stained with haematoxylin and 

 ecsin, but there are other stains which may be used to advantage 

 to bring out the inner structure more clearly. In 1904 it was sug- 

 gested to Williams^" that it might be possible to demonstrate Negri 

 bodies in smears of the brain tissue, which was tried and found to 

 be a highly satisfactory and quick method to demonstrate the bodies. 

 The smears are made by spreading over a slide, a small piece of brain 

 tissue in which the Negri bodies are most frequently found. The 

 tissue is placed upon a slide near one end and is covered with a 

 cover slip. Pressure is then applied upon the cover slip and the 

 brain tissue flattened out and spread toward the other end of the 

 slide. The smears before they are given an opportunity to dry are 

 placed in absolute methyl alcohol, one to three minutes, which, in 

 hehydrating the tissue, firmly fixes the smear upon the slide. The 

 methods of staining these smears are numerous and most all of them 

 good, providing they bring out the inner bodies and stain the struc- 

 ture surrounding these inner bodies of a different shade or color, 

 than the nerve cell in which they are found. In the laboratory of 

 the Pennsylvania State Livestock Sanitary Board, the following pro- 

 cedure in the demonstration of the Negri bodies has been closely ad- 

 hered to during the past four years: As soon as the animal's head 

 arrives at the laboratory, the entire brain and the plexiform gang- 

 lion, with its closely associated sympathetic ganglion, are removed 

 (see Plates I and 11). A portion of the cerebellum is placed in 

 sterile glycerin, in which the brain tissue may be preserved and re- 

 tain the virus fbr many weeks. These glycerin immersed specimens 

 are only referred to when the microscopic examination is unsatis- 

 factorv for the animal inoculation test. Aside from preventing de- 



