Immunity of the skin and mucous membranes 413 



H. Buclmer's inhalation experiments made with spores, and the 

 study of the organs of animals so treated, leave no doubt as to the 

 possibility of the invasion of an animal by the respiratory channels 

 by the anthrax bacillus. Furthermore, the "rag-picker's disease" 

 and the " wool-sorter's disease," or pulmonary anthrax, developed in 

 man as a result of the inhalation of dust charged with anthrax spores, 

 demonstrate most clearly that it is possible for the anthrax bacillus 

 to enter the body by the respiratory channels. The pulmonary 

 mycoses, produced by the penetration of the Aspergillus fumigatus 

 in the human subject, offer confirmatory evidence. 



In spite of the fact that the pulmonary tissue is not impermeable 

 to pathogenic micro-organisms, it is none the less true that it exhibits 

 a very marked resistance to infection by this channel. It is, however, 

 neither the thickness of the wall, as in the case of the skin and the 

 mucous membranes, nor the mechanical elimination with the help of 

 the vibratile cilia or of the secretions, that constitute the means 

 of defence in the respiratory alveoli. Here the cell elements are 

 charged with the duty of ridding the lungs as much as possible 

 of the micro-organisms which enter. Ribbert 1 and his Bonn pupils, 

 Fleck 2 and Laehr 3 , observed this fact long ago. They showed that 

 the spores of Aspergillus flavescens and the staphylococci, injected 

 into the veins or into the trachea, penetrate into the pulmonary 

 alveoli, where they are soon seized by the " epithelial cells " and the 

 leucocytes. Laehr observed that this phenomenon is produced at the 

 end of a few hours, and that the ingested cocci within the phagocytes 

 undergo a progressive degeneration and at last disappear. Tchisto- 

 vitch 4 , working in my laboratory, studied micro-organisms pathogenic 

 for the rabbit the anthrax bacillus, the coccobacillus of fowl cholera, 

 and the bacillus of swine erysipelas ingested by the "dust-cells" of 

 the alveoli. He has added the important observation (already referred 

 to in chapter iv) that these phagocytic elements are not epithelial cells [434] 

 at all, but are really macrophages of lymphatic origin. They are not 

 found in the alveoli of new-born animals, but soon appear there and 

 iustal themselves in such a manner that for long one was led to 

 regard them as true epithelial cells of the pulmonary tissue. This 

 tissue, invested with an extremely delicate covering, is incapable of 



1 "Dor Untergang pathog. Schimmelpilze im Korper," Bonn, 1887. 



2 " Die acute Entziindung der Lunge," Bonn, 1886. 



3 " Ueb. d. Untergang des Staphylococcus," etc., Bonn, 1887. 



4 Ann. de I'Inst. Pasteur, Paris, 1889, t. m, p. 337. 



