16 THE HISTOGENESIS AND GROWTH OF THE OTIC CAPSULE AND ITS 



aquaeductus vestibuli and seemed convinced that the main communication was 

 through the aquseductus cochleae as described by Weber, which view remains the 

 prevalent one to-day. 



It may be added that Retzius (1884) subsequently made some further injection 

 experiments in older fetuses and in the adult, which were published in his large 

 monograph on the ear. He found (p. 330) that in this way the scala tympani com- 

 municates freely through the ductus perilymphaticus with the subarachnoid spaces, 

 and not with the subdural space, which point had been left undecided by Weber. 

 By injecting through either the round or oval window he was able to trace the escape 

 of the fluid into the subarachnoid spaces, but never into the subdural space. 



The comparative anatomists gave relatively little attention to the connective- 

 tissue spaces around the ear and there was consequently no great advance secured 

 from this aspect of the problem. Hasse (1873, account taken from Retzius) inves- 

 tigated embryos of various mammals, but his results are confusing. Concerning 

 the lymph tracts of the inner ear he showed that in man and other mammals, in 

 embryonal and adult stages, there exists a channel to which he gave the name ductus 

 perilymphaticus, which is the same channel through which the injectionists had forced 

 their fluids into the scala tympani. Hasse described this as provided with a sac 

 which connects on the one hand with the cavum subarachnoideale (the outer epi- 

 cerebral space after splitting the brain membranes into pia and arachnoid) and 

 into a lymph-vessel on the other. This drainage path of the "perilymph, " accord- 

 ing to him, is not the only and in fact is not the chief drainage path; a similar path, 

 consisting of a funnel-shaped sheath of arachnoid, projects into the internal audi- 

 tory meatus accompanying the acoustic and facial nerves. In a later paper, Hasse 

 (1881) reverses the importance of these two channels and describes the perilymph 

 as flowing chiefly through the ductus perilymphaticus into the peripheral lymph 

 system in the region of the jugular foramen, the same channel also draining the 

 cerebrospinal fluid of the subarachnoid cistern. There is also, according to him, 

 some drainage from the subdural space through the internal auditory meatus. 



Of more importance is the description of Retzius (1884). In his large mono- 

 graph on the ear the gross and finer morphology of the periotic spaces and espe- 

 cially of the higher mammals, is described in greater detail and completeness than 

 had previously been done. The comparative embryology of the spaces is referred 

 to by Balfour (1885). He speaks of lymphatic spaces (p. 522) as forming in the 

 mesoblast between the membranous labyrinth and the cartilage. These spaces are 

 partially developed in Sauropsida, but become larger and more important in mam- 

 mals, where they form the two scalao and the space surrounding the utricle and semi- 

 circular ducts. According to him the scalse begin to develop at the basal end of 

 the cochlea, the cavity of each being gradually carried forward toward the apex of 

 the cochlear canal by a "progressive absorption of the mesoblast." 



The descriptions of Retzius (1884) and of Kolliker (1861 b, 1884) and also the 

 chapter in the sixth edition of the " Gewebelehre, " rewritten by v. Ebner (1902), 

 have had a prevailing influence on the present conception of the character and 

 development of the tissues of the otic capsule. There should be mentioned with 



