8 ARTIFICIAL PRODUCTION OF TUBERCLE. 



very largely noticed, except by M. Villemin, who describes them as frequent. 

 I believe the reason for this has been, that, to a great extent, they are seated 

 deeply in the subcutaneous tissue immediately under the hairy skin; and, 

 unless they are looked for carefully, and all the superjacent tissue removed, 

 they may easily escape observation. 



When these little granulations are examined under the microscope, they 

 are found to present the following appearances. In the centre, they appear 

 to present, for the most part, nothing but a mass of nuclei, or rather, I should 

 say, speaking my otsti conviction, of cells imbedded in a homogeneous tissue, 

 of which the nuclei alone are visible ; or it may be stated that, in this part, 

 they consist of nuclei imbedded in a homogeneous tissue. Further from the 

 centre, and Avhere their structure is less dense, these granulations may be 

 seen to consist of round, or occasionally of fusiform cells, imbedded in the 

 meshes of a fibrillated tissue, which forms bands or trabeculae, between which 

 the cells lie. The bands are of variable thickness, and are subdivided 

 into narrower bundles. A series of spaces are thus formed, which are 

 filled with rounded nucleated cells, but, in many parts, single cells having 

 this character are surrounded by this fibrous network (see Plate III. fig. 8). 

 A structure is thus produced, having the strongest resemblance to the 

 elementary composition of a lymphatic gland, or to the cytogenic tissue 

 U^ of it.' The development in this manner from the elements of the connective 

 tissue of a structure having so strong a resemblance to a lymphatic gland 

 in miniature, is a very interesting fact among this series of pathological 

 phenomena. 



Towards the circumference of these masses, and in the adjacent tissue, 

 where the reticular arrangement is less distinctly marked, fusiform cells, and 

 oval cells, often with double nuclei, may be seen in various stages of multi- 

 plication and division. 



The ordinary size of the cells constituting the granulations is from 

 l-2000th to l-3000th of an inch in diameter. Some larger cells may reach 

 a size of 1-lOOOth by l-800th of an inch. The nuclei are very uniform in 

 size — from l-3000th to l-3200th — and their outline is particularly sharp and 

 well defined. Their contents, too, are refractive and glistening. Sometimes 

 one or more nucleoli may be seen in their interior. The larger cells are 

 sometimes finely granular. They present a certain resemblance to epithelial 

 cells — a resemblance which has also been noticed by Professor Lebert. 



Throughout the granulations many of the cells, and also of the nuclei, 

 are seen in various stages of fatty degeneration. The fat is sometimes in 



' Untersuchungen iiber den Bau der Lymphdrlisen, 1860. 



