HISTOLOGY OF THE VITREOUS HUMOUR. 349 



It is clear from this that the hyaloid membrane is nothing else 

 than the limitans, which passes without interruption upon the pars 

 ciliaris retinae in front of the ora serrata, and Kolliker also holds this 

 opinion. The limitans may be easily seen in ineridianal sections 

 through the pars ciliaris retinae, supposing that the section runs 

 exactly parallel to the course of the fibres of the zonula. In such 

 preparations the limitans appears as a distinctly doubly contoured 

 line, which divides by a very sharp line the pars ciliaris retinae from 

 the zonula. 



In carefully made preparations the limitans may be detached for 

 some distance as a fine membrane., both upon the zonula and on the 

 pars ciliaris retinae. 



The views of Weber are quite peculiar, and unlike those of any 

 other author. In his opinion the whole vitreous is composed of 

 anastomosing cells forming a network, in the meshes of which a 

 mucous fluid is contained. 



Dr. Smith* has lately stated that the vitreous humour of Man, ma- 

 cerated for several days in water, and treated with carbolic acid, shows 

 a concentrically laminated structure in its peripheric portions, whilst 

 the central portion is radiated; the concentric laminae, according to his 

 account, are composed of coarse fibres, and the nucleus of stellate 

 anastomosing cells. He observed also an open canal extending from 

 the papilla optica to the posterior surface of the lens. 



Bowman had already made similar statements in regard to the 

 central portion. If the method adopted by Smith be pursued, it is 

 difficult to determine what is and what is not to be regarded as an 

 artificial product. 



The great diversities of opinion on this subject held by different 

 authors, as shown by this short historical account, are explicable on 

 the one hand by the difficulties that 'present themselves in the exami- 

 nation of the fresh vitreous ; and on the other by the differences that 

 are presented by the various methods of artificially hardening it. 



The membranes are the principal cause of discord, some maintaining 

 that all the layers of the vitreous are separated from ons another by 

 membranes, whilst others, being unable to discover the membranes, 

 deny in consequence the correctness of all the other observations. 

 Now, although the membranes are really .absent, this does not preclude 

 the possibility of the existence of a laminated structure. Thin trans- 



* D. Smith, Structure of the adult Human Vitreous Humour, Lancet, 

 19th Sept., Vol. ii., 18G8, pp. 376378. 



