PA THOLOG y 



disseminated through the body, perhaps by the blood and the 

 lymph streams. It must be remembered, however, that the 

 nature of the initial lesions is quite unknown. So enormously do 

 the bacilli multiply in the body that there are few diseases which 

 show an equal infection. 



The pathogenesis of the lesions is not very well known, and there are many 

 points of dispute which so far have not been settled. The early stages have 

 been most carefully studied by Unna in the neurolepride, in which there is 

 at first a dilatation of the capillary vessels of the skin, on the walls of which 

 the typical bacilli can be found. The organisms now pass into the wall of 

 the vessel, and appear to irritate the connective-tissue cells of the vicinity, 

 which, becoming plasma cells, surround the periphery of the vessel. 



There is a dispute as to whether any diapedesis of the white cells takes 

 place. Thus Thin and Neisser support the view of a diapedesis, to which, 

 however, Unna is opposed. According to the former observers, the cells of 

 the leproma contain not merely plasma cells, but also leucocytes and lym- 

 phocytes, while according to the latter they are entirely plasma cells and their 

 derivatives, for Unna holds the view that the bacillus has but little attraction 

 for the white cell. The organisms pass from the vessel wall into the lymph 

 capillaries, in which they grow. These early stages have not been seen in the 

 typical leproma, in which the bacilli from the first are met with in the lym- 

 phatics, in which they grow luxuriantly, causing the considerable dilatation 

 which is a marked feature of the lesion." 



Now occurs a phenomenon concerning which there is much difference of 

 opinion, for either the plasma cells increase in size, and, becoming multi- 

 nucleated, engulf the bacilli, forming in this way the typical ' lepra cells ' 

 of Virchow — a view supported also by Neisser and others — or the bacilli 

 attack the plasma cells, destroy their cytoplasm, and so damage the nucleus 

 that it becomes achromatic and breaks into several pieces, which remain sur- 

 rounded by, or on the side of, a mass of bacilli embedded in mucus, thus giving 

 rise to a false appearance of a giant cell or chorio-plaque enclosing baciLi, 

 as asserted by Unna and others. Uniia's staining method with Victoria blue 

 and saffranin colours normal bacilli blue, and dead bacilli yellow. 



The lesions show large cells — the ' lepra cells,' containing large masses of 

 bacilli — but in addition to these cells there are also masses of bacilli embedded 

 in mucus, and not enclosed in cells, which are the ' globi ' of older writers, 

 and which in fresh preparations appear as large, rounded, brownish masses. 

 Bayon believes that the bunches of bacilli arise partially by the choking of 

 the lymphatics by phagocytes swollen by the numbers of the bacilli which 

 they have engulfed, and partially by the endothelium of the vessel wall also 

 becoming distended with bacilli. The nuclei of these cells degenerate and are 

 eliminated, while the remnants of the cells, together with the bacilli, form 

 ' the globi,' and when these remnants disappear the bacilli are left free in 

 the tissues. The hyaline coating of many bacilli may be a product of the 

 protoplasm of these cells or may be secreted by the bacilli themselves. Some- 

 times typical giant cells, called ' Langhans' cells.' are seen. Marchoux and 

 Bourret consider the so-called lepra cells to be undistinguishable from the 

 large mononuclear leucocytes. 



The bacilli do not invade the surface epithelium, nor the layer of the cutis 

 directly below this; nor do they affect the sweat glands, nor the hair sheaths 

 superficial to the opening of the sebaceous glands. 



The t3rpical leproma, therefore, shows superficially epithelium, normal in 

 every respect, except that there are no interpapillary processes. Below the 

 epithelium there is a layer of connective tissue, free from bacilli, under 

 which lies the typical lesion, composed of lepra cells, plasma cells, and con- 

 nective-tissue cells, separated by a very slight amount of fibrillar connective 

 tissue, and containing vessels, whose walls are thickened by an infiltration of 

 the adventitia, media, and intima to such an extent that at times the lumen 

 may be obliterated, while the lymphatic spaces are dilated and filled with 



