220 QUARTERLY CHRONICLE. 
parts, e.g., intercellular substance, &c., are untouched. The 
fresh tissue should be covered with a little of a solution, from 
one to two per cent. of chloride of gold in distilled water, 
and allowed to stand until it assumes a straw-yellow colour. 
It should then be washed and placed in very dilute acetic 
acid (one to two per cent.). The colour will in the course of 
some hours gradually develope itself. As a general rule 
what silver salts stain gold does not, and vice versd. Hyper- 
osmic acid is difficult to obtain, and dangerous, though it 
appears to be of great use as a reagent. Vanadic acid has 
been proposed as a substitute. 
“Structure of the Iris.’—A. Gruenhagen reviews the 
anatomical evidence advanced as to the existence of a dilatator 
pupille muscle, and concludes by denying its existence in 
man and animals. He appears completely to have overlooked 
the observations of Joseph Lister published in this Journal in 
1855,in which such muscular fibres were described (Henle’s 
‘ Zeitschrift,’ vol. xxvi). 
