816 



opinion, be mounted so as to cut during the pulling and not dur- 

 ing the pushing stroke. The saw cuts sections of bone at the 

 rate of one in two to three minutes, which are sufficiently thin and 

 smooth, and only require to be washed free from sawdust to he 

 ready for mounting. The saw frame being thicker than the blade, 

 the upper part of each of the guides is set back so that the blade 



plane. Bdth blade and frame are held against the guides hy steel 

 sin iug-. the face of the guides being also protected by hardened 

 steel, securing a correct path for the saw independently of the 

 skill of the operator. For cutting soft tissues, with a razor, the 

 instrument is turned so that the cutting is done in a horizontal in- 

 stead ol a vertu d pi in. , tin oh ct In ing irrami 1 on tin sli ling 



nary work will contain a 1£ inch cube of the material to be cut, 



Recent Objectives. — Mr. Charles Brooke in his President's 

 Annual Address before the Royal Microscopical Society, makes 



in object glasses. A ••remarkably line Mb" by Powell & Leal and, 



construction is not discussed, as it has not been made known by 



Increased flatness of field has been obtained in objectives con- 

 structed on Mr. Wenham's formula, by replacing the original 

 single plano-convex posterior lens by two plano-convex lenses of 

 proportionally less curvature. Mr. Brooke possesses a |th thus 



possession. It defines well with the sixth eye-piece of Ross, which 



in certain c:i<cs beeau>e of increasing not in the simple ratio ot 

 such surfaces, but in proportion to the square of that number, as 

 if an objective with lour cemented surfaces should have four times 



