TEXT-BOOK OF BACTERIOLOGY. 249 



were clearly recognized. Any one who could have seen the prepa- 

 rations made from these experiments can scarcely have a doubt 

 but that it was a case of genuine lepra and not a case of mistaken 

 tuberculosis. 



None of these experiments decide in what manner the distribu- 

 tion of leprosy takes place under natural circumstances. We only 

 know that man himself is the chief means of conveying the virus; 

 but as to the important question whether an infection from one 

 human being to another generally occurs or can possibly take 

 place, and, if it does, how it is accomplished, opinions differ very 

 widely. 



Like tuberculosis, leprosy attacks almost all organs and parts 

 of the body; yet it exhibits a preference for the skin and the periph- 

 eral nerves. 



We may, therefore, suppose that the symptoms of the disease 

 and the conditions revealed by post-portem examination will be 

 different. Only those tubercles which have already been fre- 

 quently spoken of are usually found. Examined under the micro- 

 scope, they appear almost exactly like those of tuberculosis in their 

 composition, and macroscopically they can hardly be distinguished 

 from the latter at the beginning of their development. Giant cells, 

 jt is true, appear very rarely in the lepra tubercles, and in their 

 structure the inflammatory cells, the lymphoid elements, are al- 

 most exclusively concerned. 



It is chiefly in the tubercles that the bacilli are found, but they 

 are also found in the skin and the connective tissue surrounding 

 the nerves, and in the lymph glands, the spleen, and the liver, but 

 are generally absent in the blood. 



As to the precise distribution of the rod-cells in the tissue there 

 has been of late years much difference of opinion, and the question, 

 " Where do the lepra bacilli lie ? " has often been asked. The opin- 

 ion long prevailed that the inflammatory cells of which the tuber- 

 cles are composed were to be regarded as the chief seat of the 

 micro-organisms, and the presence of bacteria in them was regarded 

 as their characteristic and hence they were often called "lepra 

 cells.'" Unna opposed this view with the assertion that the lymph 

 ducts of the glands were the true seats of the bacilli, and that by 

 means of his desiccation method (the main facts of which have 

 been given)* the truth of his statement could be proved. 



If he dehj'drated his sections, after the decoloration in nitric 

 acid and distilled water, by heating over a flame instead of by 



* See page 57. 



