PROFESSOU HYBTIik ANATOMICAL NOTES. 317 



imperfections in the vision of minute objects, cannot hold as true for 

 all eyes, now that the existence of bloodless retinas is an established 

 fact. 



The retina then, of four classes of vertebrate animals is not nou- 

 rished by the direct intervention of the circulatory system, and 

 can be preserved in health and vigour, only by some endosmotic 

 process. 



And here I may mention, that this endosmotic action is limited 

 in birds to the choroid surface alone. In the other three classes, 

 Reptiles, Amphibia and Fish, absorption, on the contrary, may take 

 place both from it and from the hyaloid membrane. This latter 

 membrane, as I was the first to show, many years ago,* is in 

 some reptilia and amphibia a highly vascular one, and late investi- 

 gations of mine have made it evident, that the hyaloidea of all 

 fishes perfectly resembles that of the reptiles alluded to, in the rich- 

 ness of its supply of blood-vessels. The result of these investigations 

 I reserve for a special treatise on the vascularity of the hyaloidea 

 of fish. This subject is one well worth further investigation. 



2. On some peculiarities of 'the gills of Lutodeira Chanos Forsk. 



I have had an opportunity of investigating the anatomy of this 

 very rare and most valuable fish, and have discovered the following 

 modifications to exist in its respiratory apparatus, which though 

 partially found in some other clupeid and salmonoid fish, yet are 

 most fully developed only in this genus. 



Attached to the gills there is an accessory respiratory organ, pre- 

 senting the form of a tube, partly membranous, partly cartilaginous ; 

 this tube is twisted upon itself like a helix, one and a half-times, and 

 is of equal calibre throughout : its length is one inch and three quar- 

 ters and its diameter is two lines. It is situated above the fourth 



* I do not care much to claim the right of priority in scientific questions. That 

 some new fact has been demonstrated, is well; it matters not who was the happy 

 demonstrator; but I may infer, as a proof of the feeble renown of Austrian science, 

 that my discovery of the blood-vessels in the hyaloidea of reptilia and amphibia, 

 made when I was a young man (Med. Jahrbiicher des Osten. Staater, Band 15) 

 had not reached England when Mr. J. Quekett wrote bis " Observations on the 

 vascularity of the Capsule of the Crystalline Lens, especially in certain Reptilia." 

 (Trans. Microscop. Soc. of London, Vol. III. 1850).f I made the first injection of 

 the Hyaloidea of Coluber and Kana in the year 1831. The preparations are now 

 in the Anatom. Museum of our University, and duplicates were sent in 1832 to 

 Prof. Retzius in Stockholm, and 1837, to Prof. T. Midler in Berlin. 



f In a note to me, Prof. Hyrtl adds, that in all the Saurians and Chelonians 

 there is no vascular hyaloidea, and that even among the amphibia, the Sozura — 

 (Salamander, Triton, Amphuima, &c.) have a bloodless hyaloid. Professor Quekett 

 erred in mistaking the hyaloidea for the capsule of the lens. In the frog the lens 

 is very large, and the* vitreous humour very small, so that in spirit specimens it 

 almost disappears, and then the hyaloid membrane embraces the posterior portion 

 of the lens so as to be easily mistaken for a capsule. 



