520 LECTURE XX. 



tion to tubercle. But by the side of these inflammatory 

 products, or also independently of them, we find a pecu- 

 liar structure [the knot, granule] which, if they are to 

 be regarded as real tubercle, would no longer be included 

 in the ordinary classification ; and it is certainly an ex- 

 tremely characteristic circumstance that in France, where 

 the terminology of Lebert has become the prevailing one, 

 and the corpuscuks tuberculeux are wont to be regarded 

 as the necessary accompaniments of tuberculosis bodies, 

 concerning the tuberculous nature of which there can be 

 no doubt, have quite recently been set down as some- 

 thing altogether peculiar and which had hitherto re- 

 mained undescribed. For one of the best, nay perhaps 

 the best, micrographer France possesses, Robin, has, in 

 his examinations of cases of tubercular meningitis, deemed 

 it impossible to regard the little granules in the arach- 

 noid * [pia mater] which every body looks upon as tu- 

 bercles, as being really tubercles, because the dogma 

 now prevails in France that tubercle consists of solid 

 non-cellular corpuscles, and in the tubercles of the cere- 

 bral membrane cells in a state of perfect preservation are 

 met with. To such curious aberrations does this track 

 lead that one ends by being unable to find a name for 

 real tubercle ? because so many accidental objects have 

 been confounded with it, that what was sought for, or 

 even what had been found and was already grasped, has, 



* The so-called visceral (cerebral) layer of the arachnoid is only the superficial 

 layer of the pia mater -which is spread evenly over, and does not dip in between, 

 the convolutions, and being (as the name, arachnoid, implies), of a reticulated tex- 

 ture contains spaces (subarachnoid spaces). The so-called parietal layer of the 

 arachnoid is only the inner superficial layer of the dura mater with the epithelium 

 lining it. The Author employs the term arachnoid in general only for the purpose 

 of making himself more intelligible to others, but as this superficial layer of the 

 dura mater does not possess a reticulated structure and is everywhere inseparably 

 connected with the rest of the membrane, and as epithelial coverings are not wont 

 to be designated by special names, he of course always uses the term of the pia 

 mater. Such expressions, therefore, as the " sac " or " cavity of the arachnoid " 

 are incorrect. Based upon MS. Notes by the Author. 



