The Nature of the Tectorial Membrane 117 



ceivably delicate and flexible. It is by far more sensitively flexible in 

 the transverse than in the longitudinal direction and the readiness with 

 which it bends when touched or even agitated is beyond description. 

 j\Iounted bits, carefully removed, in the fresh seldom showed longitu- 

 dinal folds or crumples, but it Avas very difficult to avoid their being 

 bent upon themselves or sometimes tied into impossible knots and 

 gnarls. For the greater part, the tectorial membrane is much wider 

 and thicker than a medullated nerve fiber, for example, but the manipu- 

 lation of a fresh nerve fiber, especially under fluid, is quite an easy 

 task when compared with attempts to manipulate this membrane. 

 Again, its quality of adhesiveness is phenomenal. It is so subject to 

 surface tension that, it matters not how clean the needle point may be, 

 to touch the membrane is to have it stick, and to remove it from the 

 needle usually means totally spoiling the specimen throughout the 

 region of contact. Scraps of debris and shreds of tissue will adhere 

 to it, and, when bent upon itself, it will often cohere. The membrane 

 had to be moved chiefly by carefully inducing currents in the fluid in 

 Avhieh the work was done. 



Its specific gravity is manifestly slightly greater than that of the 

 fluid in which it normally lies. The amniotic liquor of the pig is 

 supposedly about isotonic with the blood serum and lymph of the 

 animal. When freed in this fluid, the membrane, or parts of it, will 

 remain suspended and be wafted about for several seconds, moved by 

 the slightest agitations, but gradually it comes to rest upon the bottom 

 of the dish. Bunge's Physiological and Pathological Chemistry gives 

 0.81 per cent sodium chloride solution as isotonic or physiologically 

 normal for the pig. In this solution the membrane finally sinks just as 

 in the amniotic fluid. After fixation in Zenker's fluid, it sank similarly 

 in the tap water of this laboratory. 



As delicate and flexible as the membrane obviously is, the behavior 

 of my preparations indicated that it does possess elasticity. Judging 

 from their descriptions, and especially from their illustrations, most of 

 the observers cited above did no more than to assume an elasticity for 

 the membrane from its apparent consistency and the various positions 

 and shapes it presented in their hardened preparations. Eetzius and 

 Kishi and the very few others who, in addition, observed the fresh 

 membrane in indifferent fluids, pronounced it elastic from its behavior 

 in these fluids, and the behavior of my preparations confirm their 

 observations. Because of its extreme sensitiveness and flexibilitv, one 



