The mucopolysaccharide nature of the material deposited in rabbit testes infected with Treponema pallidum was confirmed by histochemical staining with alcian blue. Differential staining of mucopolysaccharides showed the presence of sulphated mucopolysaccharides as an almost constant feature, whereas in little more than half of the orchitic testes studied variable deposits of hyaluronic acid were seen. The treponemes were almost exclusively present in the areas rich in mucopolysaccharide. A

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... nation staining with the Warthin-Starry method and alcian blue showed treponemes in close association with pre-existing fibrils and cells contained in these fibrils. The latter findings were confirmed by electron microscopy, and the fibroblasts to which treponemes adhered displayed the characteristics of activated cells. The close parallel between the histopathological changes observed here and their descriptions in published reports shows that our specific strain still behaves the same as the original Nichols pathogenic strain of Tpallidum. In thc course of syphilitic orchitis in rabbits three sequential but commonly overlapping phases can be distinguished: thc inductivc, the reactive, and the latent phases. 1 2 During the inductive phase the number of treponemes increases and a loosely woven, acellular, amorphous substance forms, which seems to be deposited between the pre-existing testicular tissues. The presence of mucopolysaccharides in these areas was likely because of metachromatic staining with methylene blue and related stains. Scott and Dammin provided evidence that these changes were specific for the syphilitic process.3 The influx of large numbers of mononuclear cells marks the transition from the inductive to the reactive phase. The latent stage is characterised by interstitial flbrosis, which is considered to be a repair mechanism. M ucopolysaccharides may be of considerable importance in syphilitic infection, as they have been Address for reprints: Dr