402 SPECIAL HISTOLOGY. 



substance, and a formation from successive deposits.* In the plexus 

 chorioidei, in the pineal gland, occasionally in the pia mater and 



* [The recent investigations of these corpora amylacea by Virchow, (see Archiv. f. path. 

 Anat. Sept. 1853) have led him to the important discovery of their true nature, viz. : that 

 they are composed of a substance, resembling the cellulose in plants. The fact that in the 

 animal kingdom, starchy substances had only been found in a low class of the invertebrated 

 animals, induced Virchow to examine all starch-like bodies occurring in the higher classes 

 of the animal kingdom, and thus the exact composition of the corpora amylacea was ascer- 

 tained. As this discovery is of great importance, I shall quote the author's own words. 



" In a histological point of view, it has often occurred to me, that the umbilical cord in 

 Man possessed a great similarity in its structure to the cellulose in the Ascidians. (See 

 Wiirzb. Verhandl. 1851, Vol. II. p. 161, note.) And I was the more confirmed in this idea 

 by Schacht's observations, so that ever since my researches have been more carefully directed 

 to this subject. But in most instances I searched in vain, as in the ova of amphibia and 

 fishes, the peculiar yelk-plates of which I described. (Zeitschrift fur Wiss. Zoologie. 1852, 

 Vol. IV. p. 240.) I was more successful, however, recently, when I directed my attention 

 to the so-called " corpora amylacea " of the brain, of the exact nature of which, as compared 

 with the other starch-like bodies in man, I had not been able to form any very definite 

 conclusions. I soon found that on the application of iodine, they assumed a bluish tint, and 

 upon subsequently adding sulphuric acid, the exquisite violet color, which is known to be- 

 long to cellulose, and which appeared the more intense, as it formed a distinct contrast to 

 the surrounding yellow or brown nitrogenous substances. 



" I have so frequently repeated these investigations, and with so many precautions, that I 

 consider the results as perfectly certain. For I have instituted comparative researches not 

 only in different human bodies, and in the most different situations, but I have allowed the 

 reagents employed to act under all possible conditions." 



The best manner, Virchow continues, to obtain this reaction is to allow an hydrated 

 solution of iodine to act on the bodies in question, and then to add a little diluted sulphu- 

 ric acid. Care should be taken not to add too much iodine at once, and to allow the 

 sulphuric acid to act very slowly. The most beautiful preparations were obtained by 

 adding a drop of sulphuric acid to the edge of the thin glass covering a preparation, and 

 allowing it then to remain undisturbed from twelve to twenty-four hours. Every precaution 

 having been taken against an accidental admixture of starch or cellulose, the following results 

 were obtained : 



"The corpora amylacea are chemically different from the concentric spherical corpuscles 

 of which the brain-sand is composed, and with which they have hitherto been confounded. 

 The organic basis of these brain sand-granules, is evidently nitrogenous ; iodine and sul- 

 phuric acid color it an intense yellow. The same is true not only of the sandy matter in 

 the pineal gland, and the choroid plexuses, but also of that of the Pacchionian granulations 

 and of the dura mater, as well as of the dentated plates in the spinal arachnoid. In all 

 these parts, except in a few spots in the pineal gland, I have never obtained the characte- 

 ristic blue reaction. It would, therefore, be henceforth advisable to restrict the term ' cor- 

 pora amylacea' to these cellulose corpuscles. 



" The cellulose granules seem to be connected with the presence of the ependyma sub- 

 stance in certain quantities, and might not improperly be considered as a part of it. But 

 how they are produced from it, it was impossible to recognize. They are usually minute, 

 scarcely corresponding in size to the nuclei of the ependyma. Can they originate from 

 these 1 ? The larger they are, the more distinctly laminated they appear. But they do not 

 exhibit anywhere a nitrogenous admixture, distinguishable by its yellow color. Their 

 centre is generally of a darker blue, and hence, perhaps, denser than their border. 



" The supposition, of these bodies being introduced from without, is the less probable 

 because a similar substance is nowhere else known. The cellulose in plants exhibits a 

 number of varieties, but this animal cellulose is distinguishable above all by its slight resis- 

 tance towards reagents; for concentrated acids and alkalies act on it more powerfully than 

 on vegetable cellulose." 



