THE NERVOUS SYSTEM. 403 



arachnoid (also in the cord), and although rarely, also in the walls 

 of the ventricles, there is furthermore met with, as a constant, 

 though pathological production, the gritty matter of the brain (brain- 

 sand). It consists of roundish, simple or mulberry-shaped, opaque, 

 mostly concentrically striated globules of 0-005-0-05 of a line, and 

 together with them of angular bodies, of a stalactitic, clavate, or other 

 irregular figure, with an uneven, botryoidal, scaly surface ; and also in the 

 form of simple, cylindrical, rigid fibres, either branched or reticular, and 

 of fine particles. The brain-sand contains principally carbonate of lime, 

 but also phosphate of lime and magnesia, and an organic substance, 

 which after the salts have been removed, for the most part perfectly 

 retains the figure of the concretion, that is to say, of a concentrically 

 laminated pale body, or as clear fibres. It is quite certain that this 

 brain-sand, when it assumes the form of elongated, branched, reticular 

 bodies, is simply developed in the bundles of connective tissue (Fig. 

 153), as, not unfrequently, in the pineal gland and in the membranes 

 of the brain ; in other cases it appears to be an independent incrusta- 

 tion on fibrinous concretions. Whilst cells impregnated with calcareous 

 matter, which Remak (" Obs.," p. 26) supposed them to be, according 

 to Harless (Mull. "Arch.," 1845, p. 354), do not exist. Lastly, also, 

 may be mentioned the Pacchionian granulations of the pia mater, and 

 ossifications of the membranes. The former, which are situated prin- 

 cipally on both sides of the falx major, on the flocculi, in the choroid 

 plexuses, &c., consist chiefly of a tough fibrous substance, not unlike 

 immature connective tissue, containing also undeveloped elastic tissue, 

 and corpuscula amylacea. The latter, which are true osseous plates, 

 occur sometimes on the inner surface of the cerebral dura mater, some- 

 times on the arachnoid, particularly of the cauda equina. 



The cellulose corpuscles were found only in the substance of the ependyma of the 

 ventricles and its prolongations, including the transparent substance in the spinal marrow de- 

 scribed by Kolliker as the " substantia grisea centralis," but not in the cortical layer of the 

 brain, or in the interior of the cerebral substance. Neither was Virchow able to detect 

 them in the brain of a child, or, as Bernard's experiments might lead us to suppose, in the 

 brain of a Rabbit, and he is, therefore, inclined to attribute to them a pathological import. 

 Similar bodies have been found, by Rokitansky in the optic nerve, by Kolliker in the retina, 

 by Luschka in the ganglion of Gasser. 



The exact chemical nature of these bodies has not, as yet, been satisfactorily ascertained. 

 They have not the pure reaction of vegetable cellulose, nor, as Donders supposes them 

 'to have, that of starch, and they might, perhaps, at present, be more properly called "amy- 

 loid" corpuscles. If boiled in water they are dissolved. 



This discovery of Virchow's is of great importance, not only with regard to the anatomy 

 of the corpora amylacea, but as establishing as an undoubted fact the existence of vegetable 

 matter as a part of the animal economy. Whether this be a pathological formation or 

 not, it is at present impossible to decide, the former is, however, highly probable, since 

 corpuscles with the same reaction have been found in certain abnormal conditions of the 

 spleen. (Vid. 170, Spleen). DaC.] 



