200 The Eye of tie Cod-fish. 



rectness of the descriptions and figures given by Dr. Hannover; 

 but I then pointed out, and subsequent investigations have 

 confirmed the truth, of my statements, that the assumed lami- 

 nated character of the vitreous body had no real existence in 

 nature, seeing that the laminee only made their appearance 

 after the eyeball had been steeped in a solution of chromic acid 

 or some other coagulating agent. 



During my antecedent investigations into the anatomy of 

 the eye — the results of which were only partially recorded in 

 my graduation Thesis, for which the Edinburgh Medical Faculty 

 awarded me the University Gold Medal in 1851 — I had followed 

 out the indications initiated by Dr. Hannover, and had thus 

 satisfied myself as to the danger of drawing hasty conclusions 

 from the occurrence of appearances so palpably the result of 

 chemical action; yet, at the same time, it should be acknow- 

 ledged that the application of chromic acid solutions has mate- 

 rially assisted us in the determination of the relations and 

 component parts of the retina, especially in the hands of Pro- 

 fessor Kolliker and Heinrich Miiller. Even here, however, as 

 will be shown in the following pages, the true characters pre- 

 sented by the individual elements of the retina have been either 

 changed or altogether obliterated ; and as regards the vitreous 

 body, the fallacy of supposing it to be made up of delicate mem- 

 branous laminas is evident from circumstances altogether inde- 

 pendent of microscopical inquiry. Thus, if several punctures be 

 made through the hyaloid covering of the vitreous mass in a 

 recent condition, its fluid contents will rapidly escape, and all 

 that we shall ultimately find left will be the external tunic and 

 a few septa or membranous prolongations from the internal 

 wall of the hyaloid, these together constituting scarcely a 

 fiftieth part of the bulk of the entire vitreous body. 



I may premise, also, in regard to the so-called choroid gland, 

 that the anciently received opinion, supported by John Hunter, 

 as to its muscularity, is still maintained by many at the present 

 day ; at least, they aver that this organ is in some way or other 

 concerned in the adjustment of the crystalline lens and vitreous 

 body to different focal distances. At a later period, Sommering 

 doubted whether it wei*e glandular, vascular, or muscular; 

 whilst Baron Cuvier, who supplied accurate descriptions of its 

 ordinary appearance in various fishes, returned to the still 

 older notion of Haller, that its structure partook more of the 

 character of a gland. Subsequently, I believe, Cuvier took up 

 with the opinion that the choroid gland was to be classed with 

 erectile tissues, but with whom this idea originated I am not 

 able to state. In later times, amongst others, Dr. Arthur 

 Jacob, of Dublin, diligently applied himself to the solution of 

 this question, but at the conclusion of his excellent article, 



