1 84 American Quarterly Microscopical Journal. 



suits from, or rather forms a part of the process of the inflam- 

 mation, an abnormal rapidity of cell-proliferation takes place 

 within the perivascular spaces; in other words, the leucocytes 

 or bioplasts (Beale) contained in the lymphatic channels, are 

 produced withy unwonted haste, and therefore with correspond- 

 ing imperfection, and the product of this rapid and imperfect 

 growth is the so-called "tubercle." 



In the foregoing propositions, I have endeavored to condense 

 the essential pathology of tubercular meningitis, so far as it ex- 

 presses itself in recognizable, structural lesions. I do not at- 

 tempt to deal with the intangible cause which determines the 

 production of tubercle; at best we can only give utterance to 

 vague conjectures. 



In addition to the lesions which I have noted above, and 

 characterized as essential, there are others which I think may, 

 with equal propriety, be regarded as consequential. Among 

 these secondary changes, the most important are, {a) the di- 

 minished caliber or obliteration of blood-vessels; {b) the trans- 

 udation of serum, and its accumulation in the cavities of the 

 brain; {c) the softening of brain substance in the later stages 

 of the disease. 



{a) Altered caliber of blood-vessels. In consequence of the 

 rapid and excessive cell growth within the perivascular canals 



DESCRIPTION OF PLATE XV. 



From a Camera Lucida Drawing by Dr. Mary F. Merglf.r. 



Fig. I. Showing a fusiform nodule of tubercular deposit, at the point where 

 the arterioles originate. The shriveled appearance of the distal portions of these 

 vessels is well shown, x 75. 



Fig. 2. A tubercule nodule in the continuity of a larger arteriole; at one point 

 (rt) the wall of the perivascular canal has apparently given way, and the tubercle 

 corpuscles are escaping. It is barely possible that the manipulations incident to 

 mounting the specimen may have produced the rupture, but I think not. At all 

 events, the perivascular wall at this point was thinned to the last degree, and would 

 very soon have yielded to the pressure of the multiplying, tubercle corpuscles. 

 X75. 



Fig. 3. A blood-vessel dividing into two branches: around these vessels are 

 seen the perivascular canals or " lymph paths," not yet very much affected by tu- 

 bercular infiltration. The actual microscopic appearance is but very slightly exag- 

 gerated. X 75. 



Fig. 4. Showing a group of tubercle corpuscles from Fig. 3 . The granular ap- 

 pearance of the cells, and the general cloudiness of the field, due to the presence 

 of granular matter, are well shown, x 375. 



