PKOPER TISSUE OF THE CORNEA ; CHEMICAL CHARACTERS. 401 



thus mechanically prevented* from thickening and altering like 

 the other fasciculi of fibres of the cornea. They thus produce the 

 peculiar appearance which the so-called fibrse arcuatse possess in 

 such boiled or acid-swollen specimens, but this does not prove 

 that there is any essential difference between these fibrse arcuatee 

 and the other fasciculi of the cornea. 



If the cornea be boiled continuously, or be heated in an her- 

 metically sealed glass tube, in an oil bath, for a long time, at a 

 temperature of 100 C., a considerable portion of its substance 

 dissolves. 



Under this treatment the membrane of Descemet remains for 

 a long period wholly unaltered, whilst even after four or six 

 hours' boiling the fibrillar substance may be completely dis- 

 solved, no elastica anterior remaining.f 



The liquid filtered from the insoluble residue gelatinizes like 

 solution of gelatine. 



The reactions of the fluid are, however, different from those of 

 ordinary solution of gelatine. Johann Miiller| considered the sub- 

 stance contained in solution to be identical with chondrin from hyaline 

 cartilage. This statement, however, has been denied. 



If the corneal gelatine were identical with the chondrin of 

 hyaline cartilage, the chondrin must be obtainable from two 

 different substances ; for the fibrillar substance of the cornea 

 has essentially different relations, in regard to water, acids, and 

 alkalies, from the matrix of the hyaline cartilage. In its 

 behaviour with alkalies it agrees far more closely with the 

 fibrils of connective tissue, but it will hereafter be shown to 

 differ essentially from these also. 



According to Kiihne the gelatine from the cornea differs 

 from ch'ondrin only in its non-precipitability with acetate of 

 lead, and the well-marked cloudiness it gives with tannic acid. 

 His || finds that the corneal gelatine differs from chondrin in 



* See A. Rollett, Berichte der Wiener Akademie, Band xxx. , pp. 6066. 



t See Schweigger-Seidel, loc. cit., p. 355. 



J Poggendorff's Annalen, Band xxxviii. , p. 513. 



Physiologische Chemie, p. 386. 



|| Loc. cit. 



VOL. III. D D 



