CONTAINED PERIOTIC TISSUE-SPACES IN THE HUMAN EMB1O<>. 17 



these also the work of Krause (1901), who studied the development of these struc- 

 tures in a number of vertebrate forms. He finds that the first traces of the 

 formation of a "perilymphatic space" occur some little time before the formation 

 of the scala tympani, in the region lateral to the utricle and saccule. At this point 

 the perilymphatic tissue becomes gradually fluidified and there arises between the 

 lateral wall of the two sacs and the cartilaginous wall of the labyrinth a large peri- 

 lymphatic space the cisterna perilymphatica to which the foramen ovale serves 

 as a direct approach. From this cistern the space-formation spreads into the 

 cartilaginous semicircular canals and simultaneously there begins the formation 

 of the scala?, resulting finally in a cavity system that incloses the entire membra- 

 nous labyrinth. Reference is made by him to the ductus perilymphaticus of Hasse, 

 which connects this system with the subarachnoid spaces. This duct opens at one 

 end in the vestibular part of the scala tympani and in the jugular fossa at the other. 

 Concerning its development, nothing further was known. 



In studying the development of the otic capsule, one is led into the general 

 question of the growth of hyaline cartilage, for which there is an extensive litera- 

 ture and which is beyond the scope of the present paper. For general papers on 

 this subject the reader is referred to those of Retterer (1900), Mall (1902), and 

 Bardeen (1910). Other papers that may be mentioned as dealing particularly 

 with the histogenesis of the skull are those of Solger (1889) and Filatoff (1906). 

 An experimental study by Lewis (1907) should be referred to, in which it is shown 

 that the production of the cartilaginous capsule is dependent upon the presence of 

 the epithelial vesicle and that a transplanted otic plate becomes surrounded by 

 cartilage derived from the tissue of the host. 



The gross morphology of the cartilaginous capsule of the ear has been described 

 for several embryonic stages in connection with the cartilaginous skull as a whole, 

 and mention may be made in this connection of the work of Gaupp (1906) and Terry 

 (1917) on certain vertebrate forms and the papers of Levi (1900) and Macklin (1914) 

 on the human embryo. The writer has also had the opportunity of studying a recon- 

 struction of the otic capsule in a human embryo 21 mm. long made by Professor 

 W. H. Lewis and one of a 43-mm. embryo made by Dr. Macklin, both of which 

 were modeled in this laboratory and have not yet been published. 



MATERIAL AND METHODS. 



The observations recorded in this paper are made on human embryos and 

 cover the period included between 4 mm. and 130 mm., crown-rump length, which is 

 approximately equivalent to the period between the fourth and the sixteenth week 

 of fetal life. The embryos were taken from the collection made by Professor Mall 

 and that now belongs to the Department of Embryology of the Carnegie Insti- 

 tution of Washington. With two exceptions they had already been prepared in 

 serial sections. In most of the stages the whole embryo is included in the sections, 

 in some of the older ones the head alone is included, and in the two specimens that 

 were especially prepared for this investigation the sections include only the region 

 of the temporal bone. In the following table are listed the embryos that were found 



