DIAGNOSIS 609 



in tap water for five minutes; (3) placed in 80 per cent, alcohol + 

 iodin (enough tincture of iodin added to give port-wine color) for 

 about twenty-four hours; (4) 95 per cent, alcohol + iodin, twenty- 

 four hours; (5) 95 per cent, alcohol, twenty-four hours; (6) absolute 

 alcohol, from four to six hours; (7) cedar oil until cleared; (8) cedar 

 oil + paraffin, 52, aa, two hours ; (9) paraffin, 52, two hours in each 

 of two baths; (10) boxing; (11) sections are cut at 3 to 6 micra, dried 

 in thermostat at 36 C. for about twenty-four hours, protected from the 

 dust, and stained according to the eosin-methylene-blue method of 

 Mallory. The important point in the technique is the time the 

 material is allowed to remain in Zenker. According to the author's' 

 experience two hours' fixation is not enough, three or four hours is 

 very good, and with every hour after five hours the result becomes 

 less satisfactory. Left in Zenker overnight the tissue is granular 

 and takes the eosin stain more or less deeply, both of which results 

 interfere with the appearance of the tiniest "bodies," especially of 

 the very delicate, tiny forms found in sections from fixed virus. 

 Another point in favor of the short fixation in Zenker is that the 

 precipitate formed by the mercury is not so great, and is more easily 

 eliminated, which is a very great help in the identification of the 

 tiniest forms. 



For routine work for diagnostic purposes the method of fixing 

 the smears in Zenker's solution and staining subsequently by the 

 eosin-methylene-blue method of Mallory is the simplest and most 

 reliable. 



Methods of Preparing Material for Laboratory Examination. Few 

 veterinarians are so situated and trained that they can make a depend- 

 able microscopic diagnosis of rabies in a dog. However, if a sus- 

 pected animal has bitten other dogs or cattle, horses, persons, etc., a 

 definite diagnosis should always be made, so that the proper measures 

 can be taken if the animal did suffer from rabies. One of the worst 

 things to do if a suspicious dog has bitten a person is to kill the dog 

 at once, because in the very earliest stages of rabies it may be impos- 

 sible to find the Negri bodies, yet the dog may have had rabies and its 

 saliva may already have been infective. The proper thing to do is to 

 isolate and safely detain such a dog and to watch for the development 

 of symptoms. If the animal sickens under typical symptoms of rabies 

 it may be killed and the brain examined microscopically, or if the 

 symptoms are not clear it may be allowed to die and then the brain 

 should be examined. The veterinarian in charge of the case should 

 make a postmortem examination on the dog and the head should be 

 severed from the body somewhere in the middle of the cervical ver- 

 tebrae, so that the upper cervical ganglia are left undisturbed, that 

 they may, if desirable, be included in the microscopic examination. 

 The head should then be wrapped in a piece of cheese cloth, or, if 

 available, in a thin rubber sheet, as used in surgical dressings, placed 

 in a tin bucket, then in a wooden box, and forwarded by express 

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