The Eye of the Cod-fish. 199 



cus spiralis, Pinnularia nohilis, Stauroneis Plmnicenteron, Su- 

 rirella splendida, and Cymatopleura solea. 



Here we must finish our day's work, having arrived at the 

 railway station, from whence we proceed home with our trea- 

 sures. The work of collecting has been finished, yet much 

 remains to be done before the material is cleansed and mounted 

 on slides for microscopical investigation. 



Let us hope our fatigue has not been in vain, but that the 

 store of riches we have collected together, will furnish us with 

 ample material for much interesting study and instruction. 



THE EYE OF THE COD-FISH. 



BY T. SPENCER COBBOLD, M.D., F.L.S., 



Lecturer on Comparative Anatomy, Zoology, and Botany, at the Middlesex 



Hospital Medical College. 



From the earliest periods of physiological inquiry, the organ 

 of vision, especially in connection with man and the higher 

 animals, has uninterruptedly occupied the attention of the 

 anatomist, the physicist, and the philosopher; and yet, not- 

 withstanding the instructive teachings of a most voluminous 

 eye-literature, there remain difficulties to be solved both as 

 regards the visual functions of the organ and the structural 

 elements concerned in the production of its optical effects. In 

 the view, therefore, of contributing something towards our 

 knowledge of the histological peculiarities found to occur in 

 the eye of fishes, I hereby propose to dwell more particularly 

 on the existence of certain parasitic vegetations in the sclerotic 

 coat, on the structure and functions of the so-called choroid 

 gland, and on certain artificially-produced phenomena in con- 

 nection with the cones of the retina. 



Recent discoveries respecting the microscopical anatomy of 

 the vertebrate eye have, in most instances, resulted from ex- 

 aminations of the eyeball after it has been immersed for a 

 greater or lesser period in solutions of chromic acid. This 

 method appears to have originated with Dr. Hannover, of 

 Copenhagen, who published a series of papers on the subject 

 in Muller's Archiv, during the year 1845. In 1851, Dr. 

 Hannover came over to this country, bringing with him a 

 number of preparations illustrative of his recorded views as 

 to the structure of the vitreous humour in different orders of 

 mammalia; and at a. meeting of the Physiological Society of 

 Edinburgh, I had an opportunity of examining them attentively. 

 These choice preparations unequivocally demonstrated the cor- 



