398 SPECIAL HISTOLOGY. 



the tubes of the lens are those which exist on the anterior 

 half of the capsule and the starting point of the formation of 

 the lenticular elements, according to my observation, is the 

 entire anterior surface and the border of the organ. Nuclei are 

 visible in the tubes even in the lens of the adult, as was 

 known to Harting, though only at its margin. 



[With respect to the vessels of the foetal eye, Dr. Thiersch 

 has quite recently communicated to me a mass of interesting 

 details, accompanied by beautiful injections, to which I shall 

 refer in the concluding part of my f Microscopical Anatomy/ 



Investigation of the visual organ. The fibrous tunic of the 

 eye should be examined in the recent condition, and in moistened 

 sections of dried preparations, which latter, especially of the 

 cornea and at its point of transition into the sclerotica, afford 

 very useful information. If, after the removal of the vitreous 

 body and lens, the iris and choroid are dried, their connexion 

 with each other and with the fibrous tissue may be studied. In 

 order to view the nerves and vessels of the cornea, the latter is 

 removed by a circular section in the recent eye, together with 

 the margin of the sclerotic, the whole is divided into three or 

 four segments, which, in order that they may lie the better, 

 have little incisions made into them around the edge, are 

 moistened with the aqueous humour, and covered with a thin 

 plate. The nervous trunks, which are here usually opaque, 

 are then sought for at the border of the cornea, first with a low 

 power, and afterwards traced under a higher. The nerves are 

 beautifully displayed in the eye of the Rabbit, where lean perceive 

 their trunks with the naked eye, though they may usually be 

 readily found in other eyes also, but are always traced with 

 difficulty towards the centre. If the epithelium is cloudy, it 

 must be removed by caustic soda, which at first does not affect 

 the nerves. The vessels under these circumstances are usually 

 full of blood, and consequently present no difficulties. The 

 corneal epithelium is visible on the surface in sections of dried 

 preparations, and is very well shown when the surface is scraped. 

 The "membrane of Demours" is very distinct in sections, 

 and frequently its epithelium also ; otherwise the latter is well 

 seen on the surface and in detached shreds of the membrane. 

 The passage of this membrane into the ligamentum pectinatum 



