II. — Observations on the Vascularity of the Capsule of the Crystalline 

 Lens, especially that of certain Reptilia. By John Quekett, 

 Esq., Assistant Conservator of the Museum, and Demonstrator 

 of Minute Anatomy at the Eoyal College of Surgeons of 

 England. 



(Read January 13th, 1847.) 



There are certain tissues in vertebrate animals that have been 

 termed non-vascular, that is, tissues in which in the healthy state no 

 vessels carrying red blood have hitherto been discovered ; amongst 

 these are classed, by most observers, the cornea, the capsule of the 

 crystalline lens, and the vitreous humour or body. Before the adop- 

 tion of the theory of nutrition and growth by the agency of cells, the 

 existence of vessels far too minute to carry red blood, but which 

 allowed lymph and serum to traverse them (hence called vasa serosa) 

 was inferred, but as yet such vessels have never been satisfactorily 

 demonstrated. 



Many mistakes have arisen from the circumstance of certain of 

 these tissues having been examined at one time in the growing state, 

 at another when diseased, in both of which cases, blood-vessels are 

 not unfrequently present, but in the adult and perfectly healthy 

 state, such tissues have no vessels in their interior, but in their im- 

 mediate neighbourhood only. We have examples of this kind in arti- 

 cular cartilage, which in the growing state is vascular and nourished 

 by synovial membrane ; in the cornea again, the vessels are supplied 

 from the conjunctiva, as has been admirably shown by Mr. Toynbee. 

 It is now, however, well known, from the researches of Schleiden 

 and Schwann, that all tissues are developed from cells, and the re- 

 searches of Mr. Toynbee go to show that as long as the true cell-form 

 remains, these structures require vessels in their neighbourhood only. 



If we examine an injected eye of a young animal, we shall find (if 

 the injection have been successfully performed) that the posterior 

 layer of the capsule of the lens, is largely supplied with blood- 

 vessels, derived from an artery running through the vitreous humour, 

 and called the arteria centralis retina. If, however, the animal be an 

 adult, the capsule can rarely, if ever, be injected; this holds good in 

 the human subject and in Mammalia generally, but one of the prin- 



TRANS. MIC. SOC. VOL. HI. C 



