CONTAINED PERIOTIC TISSUE-SPACES IN THE HUMAN EMBRYO. 13 



Kolliker is the first to describe in some detail the formation of the otic capsule 

 and the pcrilymphatic spaces. The summary here given is taken from the second 

 edition of his book (Kolliker, 1879), in which there is some amplification of the 

 account given in the first edition. According to him, after the otic vesicle reaches 

 a certain degree of development it is surrounded by a delicate connective-tissue 

 membrane and there is an outer thicker and firmer mass which takes on the 

 nature of cartilage, which in 19-mm. cow embryos forms an integral part of the 

 wall of the skull. In human embryos 8 weeks old the labyrinth capsule consists 

 of true cartilage and completely fuses with the base of the skull. He expresses the 

 opinion that the cartilago petrosa is laid down exactly in the same way as the other 

 parts of the lateral walls of the skull and that its special characteristics, subsequently 

 assumed, are due to the presence of the special sense-organ. 



In connection with the origin of the cavities of the bony labyrinth, Kolliker 

 draws attention to the problem of space formation in general and points out that 

 the space in the otic capsule is of the type seen in the subarachnoid and other serous 

 cavities. He describes how, along with the growth of the epithelial part of the 

 labyrinth, there is also a rapid growth of its connective-tissue coverings, which soon 

 attain considerable thickness. At the same time the periotic tissue becomes differ- 

 entiated into three layers, of which the middle one soon becomes the thickest. This 

 layer consists of a network of anastomosing connective-tissue cells (Gallertgewebe) , 

 whose rounded meshes are filled with fluid. From this there is gradually formed the 

 cavity that surrounds the semicircular canals, the meshes becoming larger and finally 

 coalescing. In the process of coalescence, parts of the cellular net are broken and 

 other parts are pressed against the walls of the space, where, even in the adult, one 

 can recognize remnants of the broken net. The same process takes place in the 

 semicircular canals, the vestibule, and the cochlea. In the last-mentioned there are 

 formed the two scalse, in which, in addition to the coalescence of the spaces of t he- 

 network, there is also involved a disproportionate growth in respect to the cochlear 

 duct and the surrounding cartilage, the latter retracting from the former by virtue 

 of its rapid growth. Kolliker's conception of this process is purely mechanical, and 

 it hypothesizes a protoplasmic network that is entirely passive. He did not con- 

 ceive of an adaptive activity on the part of the protoplasm itself by virtue of which 

 the characteristic changes in form are brought about, as is to be described in the 

 present paper. 



Among a series of miscellaneous notes concerning the development of the mam- 

 malian labyrinth appended at the end of Kolliker's chapter, there is a reference as to 

 the relation of the growth of the cartilage to the growth of the contained spaces, 

 which is particularly interesting, as it shows that he hael in mind one aspect of the 

 problem with which we are concerned. He notes there (p. 746) that at first the 

 epithelial part is directly surrounded by young cartilage, or better, a cartilage-like 

 substance of which the greater part becomes subsequently converted into cartilage. 

 In its further differentiation the tissue lying directly against the labyrinth becomes 

 fibrous tissue and the tissue farther away becomes cartilage. Out of the uniform 

 fibrous tissue there is further differentiated the inner perichondrium, the fiber wall of 



