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 nourished 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,[1] is in some reptilia and amphibia a highly vascular one, and late investigations of mine have made it evident, that the hyaloidea of all fishes perfectly resembles that of the reptiles alluded to, in the richness 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, presenting 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 quarters 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. Jahrbücher 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).[2] I made the first injection of the Hyaloidea of Coluber and Rana 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. Müller in Berlin.
- ↑ 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.
