326 TUBERCULOSIS AS A TYPE OF BACTERIAL DISEASE 



1. Miliary, which were about the size of millet seeds, and 

 generally occurring in groups. 



2. Crude, miliary tubercles in yellow masses. 



3. Granular, similar to the last, but scattered. 



4. Encysted, a hard mass of crude tubercle with a fibrous or 

 semi-cartilaginous capsule. 



The " tubercle " possesses a special structure, although it is not 

 always apparent, and certain cell-forms occur in it and give it a 

 more or less characteristic appearance. 



The typical lesion is a nodule of granulation tissue, as small as 

 the size of a millet seed. The centre consists of one or more 

 multinucleated cells known as giant cells, immediately surrounded 

 by a zone of slightly elongated cells with a somewhat faintly-staining 

 nucleus, termed epithelioid cells, owing to their origin. These cells in 

 their turn are surrounded by another zone of small round cells which 

 have but little cell protoplasm, yet contain a deeply-staining nucleus, 

 and are known as lymphoid cells. They are apparently identical 

 with lymphocytes. The whole nodule is inflammatory tissue pro- 

 duced as a result of the action of a specific irritant, namely, the 

 tubercle bacillus. 



It was not till 1865 that the specific nature of tuberculosis was 

 asserted by Villemin. Burdon Sanderson (1868-9) in England con- 

 firmed his work, and it was extended by Cohnheim, who a few years 

 later laid down the principle that all is tubercular which by trans- 

 ference to susceptible animals is capable of inducing tuberculosis, 

 and nothing is tubercular unless it possesses this property. 



Klebs (1877) and Max Schiller (1880) described masses of living 

 cells or micrococci in many tubereulovis nodules in the diseased 

 synovial membrane of joints and in lupus skin. In 1881 Toussaint 

 declared that he had cultivated from the blood of tubercular animals 

 and from tubercles an organism which was evidently a micrococcus, 

 and in the same year Aufrecht stated that the centre of a tubercle 

 contained small micrococci, diplococci, and some rods. But it was 

 not till the following year, 1882, that Koch discovered and demon- 

 strated beyond question the specific Bacillus tuberculosis. 



It is now held to be absolutely proved that the introduction of 

 this bacillus, or its spores, is the one and only essential agent in the 

 production of tuberculosis. Its recognised manifestations in the 

 body of man are as follows : — Tuberculosis in the lungs = acute or 

 chronic phthisis ; in the skin = lupus ; * in the mesenteric glands = 

 tabes mesenterica ; in the brain = hydrocephalus ; in lymphatic 

 glands = scrofula.* 



The disease may occur generally throughout the body, or it may 



* There are, obviously, differences of virulence between these conditions and 

 pulmonary tubercle. 



