130 Irving Hardest}- 



above; and an outer, comprising all of the outspanning portion and thus 

 including Hensen's stripe. 



Also, throughout the literature, occur descriptions of various lines 

 and markings of the under surface in addition to Hansen's stripe and 

 the line of impress of the labium vestibulare. Hensen's stripe has even 

 been given various appearances, various widths and varied occurrence. 

 Dupuis, '94, Avorking with the tectorial membranes from the dog, cat, 

 rabbit and guinea pig, found Hensen's stripe apparently absent in some 

 cases, while in others it seemed to be represented by three lines, which, 

 however, he thought might have been due to optical defects produced 

 by the variations in the thickness of the membrane compressed under 

 the cover glass. Various extra lines have been described upon the 

 under surface of the memtoane, some running longitudinally, others 

 transversely or obliquely. Only recently, Kolmer, '07, working with 

 various mammals, including the pig and man, describes a small piece 

 of the membrane, giving it longitudinal lines upon its under surface 

 which he interprets as bundles of longitudinally running fibers. In all 

 of my preparations which proved to be shrunken, extra lines were always 

 apparent; The prevailing direction of these was always longitudinal, 

 and most of them appeared on the under surface. Especially, in all 

 those pieces which I attempted to dehydrate and clear in oil, numerous 

 lines were apparent, some of which ran obliquely and many of which 

 anastomosed. Comparison with the fresh preparations and with those 

 fixed with apparently little or no shrinkage made it very evident that 

 these extra lines were due to the shrinkage effect of the reagents, and 

 they were explained as crumplings and crimps of the shell-like peripheral 

 condensation which is seen in all sections of embedded material and is 

 probably produced in the first attack of the reagents upon the matrix 

 of the membrane. Further shrinkage or extraction of water from the 

 interior can but result in crimps of this outer, already condensed laA^er. 

 As Kolmer says, such lines always seem to stain more deeply than the 

 adjacent material, but this must be due to their greater condensation, 

 and therefore greater capacity for holding stain. Though seeming more 

 or less amorphous, as do all condensations of the membrane, a fibrous 

 structure may be detected in them; but neither in these lines nor in 

 any parts of the tectorial membrane of the pig have I been able to 

 distinguish any longitudinally running fibers. 



The normal markings readily detected on the under surface of the 

 tectorial membrane of the pig when removed intact and unshrunken, 



