10 ARTIFICIAL PRODUCTION OF TUBERCLE. 



The chief changes which can be observed by the microscope in the 

 lymphatic glands are, that there are large agglomerations of cells in groups 

 in the cortical substance, apparently cramming up the loculi with structures 

 precisely resembling the ordinary lymphatic cells, but much more densely 

 packed ; and these in some places have undergone fatty degeneration. At 

 other parts, there are large tracts which have undergone a fibroid change. 

 Among the meshes of fibres in these parts are cells which are not distin- 

 guishal)le from the ordinary lymphatic cells ; but both in these, and also in 

 the parts where the cells are denser, larger cells may be found, of 1-lOOOth 

 to l-2000th of an inch in diameter, containing one or more nuclei, and 

 often undergoing a fine molecular degeneration. 



The next organs in which changes are most frequently found are the 

 lungs (Plate I. fig. 1). The chief state I have to describe consists in these 

 organs being permeated more or less thickly by scattered granulations. These 

 vary in size from a millet-seed to a hemp-seed. Some are very small, minute 

 specks, scarcely visible by the naked eye, and all gradations can be found 

 between the smaller and the larger. They are generally scattered, but are 

 sometimes confluent in groups. Sometimes larger groups are confluent, 

 especially at the edges of the lobes ; but even in these there is more or less 

 evidence that they have been originally composed of distinct granulations. 

 The granulations do not project much from the cut surface, and they blend 

 more or less intimately mth the surrounding pulmonary tissue. They are all 

 marked by a peculiar, semi-transparent, hyaline, cartilaginous-looking margin, 

 and a cheesy centre. Some of the smallest may be found semi-transparent 

 throughout. They are firm, and they tear with difficulty from the surrounding 

 pulmonary tissue. As a rule, the centre is only cheesy, not soft ; but, in some 

 marked instances, where they have attained the size of a small pea, I have 

 observed them with a distinct softened centre, which, when evacuated, left 

 a distinct cavity. Lebert,' in one of his observations, found them breaking 

 down into cavities of considerable size. They are more common on the pleural 

 surface than deep in the lung, but are distributed pretty equally, not prepon- 

 derating in one lobe more than in another. Sometimes, when there is a group 

 of these granulations clustered together, an appearance is presented, which is 

 also occasionally seen in the tubercle of the human lung, of a fibrous network 

 running between the granules, as if the intervening tissue was becoming 

 fibrous. In addition to this, there is sometimes a general induration of the 

 lung-tissue, affecting, in a variable degree, the whole organ. Signs of pneu- 

 monia, and of general infiltration independent of the granulations, is exceed- 



* Vircliovv's Arcliiv, xli. 



