The Bacillus tuberculosis. 



129 



large, flat cells. These are the so-called endothelial cells; they are 

 nucleated and closely united at their periphery with one another so 

 as to form those sheaths which envelop the above-mentioned fibrillar 

 bundles, and thus at the same time form the lining for the spaces 

 between them. All that can be seen of these endothelial cells are 

 the nuclei, which appear either round, spindle-shaped, or curved, 

 according to the direction in which the bundles are cut, and these 

 are the cells seen in our preparations. 



In the specimen from the cat we see the nuclei of the endo- 

 thelial cells at more or less definite intervals and generally of fusi- 

 form shape; some few round or irregular -shaped cells are also seen 

 in the lymph -spaces of the connective tissue, and these are either 

 desquamated endothelial cells or free white blood-corpuscles. 



In the specimens from the rabbit the same appearances are ob- 

 served, but the quantity of free, round, and irregular cells is consi- 

 derably larger, and they are frequently seen to block up the lymph- 

 spaces. Of spindleshaped cells fewer are seen than in the cat. The 

 source of the numerous round and irregular -shaped cells must be 

 considered similar to the few seen in the specimen from the cat. 

 Comparing a large number of sections taken from corresponding parts 

 of the bodies of rabbit and cat, it is also distinctly seen that the 

 lymph-spaces are on the average decidedly narrower and fewer in the 

 rabbit than in the cat. The perivascular spaces are, however, equally 

 free and similar in both. 



The filling of the lymph-spaces with desquamated and germina- 

 ting endothelial cells, or with wandered -in white blood -corpuscles, is 

 a well-known fact in the pathological histology of tuberculosis, but it 

 does not seem to be known that this is a normal condition in the 

 rabbit and guinea-pig and in scrofulous persons long before tubercular 

 disease ensues. Under conditions to be mentioned later, these peculi- 

 arities may be, however, occasionally less marked. In general, it may 

 be said that the distinction is certainly definite enough. Any one 

 familiar with the use of the microscope can distinguish the variance 

 in the two tissues by the shape and quantity of cells, if not by the 

 size and shape of the lymph -spaces, the latter requiring more ex- 

 perience. 



Internationale Monatsschrift für Anat. u. Hist. I. 9 



