5. =Negri Bodies of Rabies.= Examine in smears or make sections. Take portions of gray brain-substance from the cortex in the region of the fissure of Rolando (in the dog from around the crucial sulcus), from the hippocampus, and from the cerebellum. Smear cover or slide by taking a thin slice of the gray matter and compressing it between two slides, or cover and slide, or by drawing the cover across the cut surface in order to get some of the cells. Dry in the air; stain with watery methylene-blue; wash; stain with watery acid fuchsin; wash in water; blot dry; mount in balsam. Negri bodies fuchsin-red (about size of red blood cells); everything else blue. When dried in the air and then fixed in methyl alcohol for 5 minutes the smears may be stained by Giemsa’s method. For the demonstration of the bodies in sections fix in Zenker’s, imbed in paraffin, and stain by the eosin-methylene-blue method. The bodies take the eosin stain. Formol fixation, freezing-microtome and Romanowsky stain give quick results. _Mann’s method_ for the staining of Negri bodies in sections is strongly recommended by many workers. Fix material in mercuric chloride or Mann’s fluid (1 grm. picric acid and 2 grms. tannin dissolved in 100 cc. concentrated water solution of mercuric chloride) for 24 hours; wash thoroughly in running water; imbed in paraffin. Stain in Mann’s mixture (1 per cent aqueous methyl-blue [not methylene-blue] 35 parts, 1 per cent aqueous eosin 35 parts) for 24 hours; wash in water; rinse in absolute alcohol; place in alkaline alcohol (absolute alcohol 50 cc., 4 drops of a 1 per cent solution of sodium hydroxide) for 15-20 seconds until sections become reddish; wash quickly in alcohol; wash about 2 minutes in water until superfluous color is removed; place in weak acidulated water (acetic acid) 1-2 minutes until sections are blue; quick dehydration in alcohol; xylol; balsam. Cells are blue, nucleoli and blood-vessels red; Negri bodies bright red. For quick diagnosis use acetone fixation and imbedding, stain in Mann’s fluid 2-4 minutes, and proceed as in the Mann’s method. While these bodies possess a great diagnostic importance for rabies, their exact nature must still be regarded as unsettled; they are most probably not parasites. 6. =Vaccine Bodies.= Fix in Flemming’s, mercuric chloride or Zenker’s; imbed in celloidin or paraffin. Stain with Heidenhain’s iron-hæmatoxylin (bodies black) or Biondi-Heidenhain mixture (bodies blue, nuclei of leukocytes and mitoses green, nuclei of epithelium and connective-tissue blue, protoplasm and connective-tissue red). These bodies are probably not parasites, but may be products of cell-degeneration.