CHAPTER XXVII. 343 



For the methylen blue method see particularly 345. 



Negative images of the corneal cells are easily obtained by the 

 dry silver method (KLEIN). The conjunctival epithelium should 

 be removed by brushing from a living cornea, and the corneal surface 

 well rubbed with a piece of lunar caustic. After half an hour the 

 cornea may be detached and examined in distilled water. 



In order to obtain positive images of the fixed cells the simplest 

 plan (RANVIER) is to macerate a cornea that has been prepared as 

 above for two or three days in distilled water. There takes place a 

 s econda ry impregnation . 



The same result may be obtained by cauterising the cornea of a 

 living animal as above, but allowing it to remain on the living 

 animal for two or three days before dissecting it out, or by treating 

 a negatively impregnated cornea with weak salt solution or weak 

 solution of hydrochloric acid (His). 



But the best positive images are those furnished by gold chloride. 

 RANVIER prefers his lemon- juice method. It is important that 

 the cornea should not remain too long in the gold solution, or the 

 nerves alone will be well impregnated. 



ZAWARSIN (Arch. mik. Anat., Ixxiv, 1909, p. 116) removes the 

 membrane of Descemet for study in the following manner. A 

 cornea, fixed in sublimate, is dissected out and put for some hours 

 into a mixture of alcohol and. ether. Then collodion of 4 per cent. 

 is poured on to the inner surface, and after some time a layer of 

 collodion with the membrane attached can be peeled off, and the 

 collodion removed from the tissue by a mixture of alcohol and ether. 



See also ROLLETT, in Strieker's Handb., pp. 1102, 1115, or previous 

 editions ; TARTUFERI, Anat. Anz., v, 1890, p. 524, or previous 

 editions ; CIACCIO, Arch. ital. Biol., iii. p. 75 ; and RENAULT, 

 C. R. Acad. Sc., 1880, p. 137. 



726. Crystalline. GERHARDT (Zeit. wiss. Mik., xiii, 1896, p. 306) 

 hardens the lens for one or two days in 4 to 10 per cent, formalin ; 

 it is then easily dissociated with needles into its fibres. 



RABL (Zeit. wiss. ZooL, Ixv, 1898, p. 272) fixes the enucleated eye 

 for half an hour in his platinum chloride or picro-sublirnate, 75 

 and 70, divides it at the equator, and puts the anterior half back for 

 twenty-four hours into the fixative. 



For Maceration you may use sulphuric acid, 533. 



See also ROBINSKT, Zur Kenntniss d. Augenlinse, Berlin, 1883. 



