Granuloma formation around the lycopodium was macroscopically and microscopically compared with the granuloma around Schistosoma japonicum eggs to determine whether lycopodium power could be used as a substitute for the eggs. The eggs were isolated from the liver and intestine of rabbits 8 weeks after infection with S. japonicum. Approximately 100, 000 eggs or 200, 000 lycopodia were injected into the lungs of each rabbit through the auricular vein. The lungs were removed 14, 28, 84 and 86 days after the injection. Paraffinembedded sections of the lungs were stained with hematoxylin-eosin, azanmallory and luna stains. Tubercula were grossly observed in the lungs of 4 rabbits at 14 days; one of which was after a lycopodia injection. The characteristics of the lycopodium tuberculum were similar to the characteristics of the egg tuberculum. Microscopically, two types of reactions developed around the eggs. One was very severe and the other was mild or absent. The severe granulomas were large in size at 14 days, but they gradually became smaller, although they were still present after 86 days. The granulomas with mild reactions were very small in size at 14 days, diminished in size with time, and disappeared by 86 days. With all types of injections, the majority of the inflammatory cells in the granuloma were mononuclear cells with some eosinophils and pseudoeosinophils. Giant cells were often observed at 14 days and they slowly increased in number. The giant cells were observed in most of the granuloma at 86 days. Scar formation was seen at 28 and 86 days. The charac teristics of the lycopodium granuloma were very similar to the characteristics of the egg granuloma except that lycopodium granuloma was smaller in size and had more giant cells, the rate of destruction and absorption of the giant cells in the tissue was also slower. Although the lycopodia did not induce as severe a reaction as the eggs, it can be assumed that the lycopodium could be used as substitute for the S. japonicum eggs under certain conditions.
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