12 THE HISTOGENESIS AND GROWTH OP THE OTIC CAPSULE AND ITS 



that was confirmed later by other embryologists. He also found that in sheep and 

 calf embryos the lamina spiralis is hollow, constituting a spiral tube that is closely 

 attached to the bony walls of the cochlea. He evidently had before him the ductus 

 cochlearis. He supposed, however, that the seal* in their formation flattened out 

 this hollow tube, thereby converting it into the lamina spiralis, and thus he did not 

 grasp the meaning of the structure and just missed being the discoverer of the mem- 

 branous cochlea. 



The significance of the spiral tube seen by Huschke in the embryo and its per- 

 sistence as the ductus cochlearis in the adult remained to be pointed out by Reissner 

 and Reichert in a series of communications published in the years 1851 to 1854, being 

 based in large part on embryological studies of the chick and also of mammals. 

 The first communication was the Dorpat dissertation of the former, completed in 

 Reichert's laboratory. It contained an account of the ductus cochlearis (canalis 

 cochlearis), which was shown to exist as a definite canal in the adult mammalian 

 cochlea. It was pointed out that the membranous part of the lamina spiralis forms 

 one-half of the wall of the canal and that the other half consists of a very thin and 

 delicate membrane that is usually torn in the preparation of such a specimen. This 

 portion has since been known as the membrane of Reissner. 



Reissner and Reichert demonstrated the complete canal in infants at about 

 term. In the embryo they found that the cochlear duct opens into the membranous 

 vestibule, but whether or not it does this in the adult was not definitely determined. 

 They give an account of the development of the ear in the chick, and they describe 

 the formation of a labyrinthine groove in the skin and how this subsequently invagi- 

 nates to become the otic vesicle to which the acoustic nerve attaches itself later. 

 They divide the early labyrinth into three chief parts: (1) recessus labyrinthi; (2) 

 vestibule and its three canals; (3) cochlear duct. In a later paper Reissner (1854) 

 refers to the formation of the scalae. He explains them as two accessory cavities 

 that are formed because the cartilage recedes from the upper and lower surfaces of 

 the cochlear duct. He denies the existence of any communication between the 

 vestibular cistern (Hohle des Vorhofs) and the scala vestibuli both in the embryo and 

 adult. His observations concerning the scalaB have proved to be less important than 

 those on the embryology of the otic vesicle and the discovery of the cochlear duct. 



Kolliker (1854) had just at this time written the first edition of his "Gewebe- 

 lehre" and had described at some length the finer structure of the cochlea, embody- 

 ing his own and the important observations of Corti (1851). He makes mention of 

 Reissner's dissertation, but there is no evidence that he appreciated at that time the 

 significance of the cochlear duct. In a separate paper and in his text-book on human 

 embryology, both of which appeared soon after this (Kolliker, 1861 a and b), he 

 definitely establishes the existence of Reissner's membrane and that it forms the 

 boundary of the cochlear canal. He confirmed the Reissner and Reichert embry- 

 ological studies showing that the cochlear canal is originally an epithelial tube which 

 is derived from the primitive ear- vesicle and hence from the ectoderm of the embryo. 

 He designates the cochlear canal as the scala media, a term which persisted for 

 many j^ears, though its inapplicability was promptly pointed out by Reichert (1864). 



