PRACTICAL NOTES ON HISTOLOGY. 233 



then in clove oil, then in cacao butter, melted at a temperature of 

 35° C., 95° F., for four to six, or even twelve hours. At the end of 

 this time it should be embedded in cacao butter as usual. When 

 hard, detach with a sharp scalpel the sclerotic and part of the 

 choroid, and leave the retina and other part of the choroid to be 

 cut in sections, whilst the rod layer has never been tampered with. 

 Fix the retina by pouring over it a little more melted cacao 

 butter to replace the mass cut away. Very thin sections can be made, 

 and had better then be put on the slide and diffusely stained and 

 mounted as follows : — -A few drops of an alcoholic solution of 

 eosin are poured over the mass and at once soaked in it ; in a few 

 minutes the mass is partially dried with blotting-paper. Heat the 

 slide to a temperature of 35S C, 95^ F. Remove the melted cacao 

 butter as far as possible with blotting paper, and add a drop or 

 two of clove oil to remove the remainder. When sections are 

 cleared drop on the balsam. It is very important to remove as 

 much of the cacao butter as possible before adding the oil, because 

 the oil often acts very violently, and destroys the section. In 

 fact, the great value of osmic acid and chromic acid as hardening 

 agents is the great hardness they give the retina, the sections 

 from which are not damaged by clove oil. The beat sections may 

 be got by this last method, used as an aqueous solution and 

 stained in bulk by Kleinenberg's or Gibbes' logwood, and infil- 

 trated and embedded in cacao butter. 



Bibliography.— " Comptes rendus," 80, p. 137. "Strieker's 

 Histology," p. 1,115, Ibid., 1873—75. " Archiv. Mik. Anat.," 

 66, p. 179 and iSSr, Ibid., 1866. "J. Anat. and Physiology," 

 79, p. 139. " Ranvier, Traite' de Technique." " Q. J. M. Sc," 

 1886. " Schafer's Histology." " Juler, Ophthalmic Science and 

 Practice." " Pollock's Histology and Pathology of Eye " (Atlas), 

 and " Klein's Atlas of Histology." 



