36 



p. KIDD. 



1st. To place the tissue to be cut, in absolute alcohol for 

 a few minutes previously, so as to render it as hard as 

 possible. 



a. Brass cylinder. 



b. Brass plate turning on a screw. 

 b'. Inner plate of glass or brass. 



c. Clamp. 



s. s. Screw moving c. 



d. Index. 



2nd. To draw the razor or knife quickly across the flat 

 inner plate (J'), to prevent tearing the tissue. 



The plate (6') on which the razor rests may be either of 

 brass or, better, of glass, as the latter is less liable to 

 become nicked and so blunt the razor. 



This microtome may be purchased of F. Maier, 9, Kramer 

 Gasse, Strasburg. The price is £1 if the flat plate {h') is 

 made of glass, \%s. if it is of brass. Different sizes can be 

 had, but the medium size here described is the most conve- 

 nient for ordinary purposes. 



Engelmann on Contractility and Double Refraction. 

 (Pfliiger's 'Archiv,' Bd. XI, p. 432) By P. Kidd, B.A. 



After referring to Boeck's original discovery of the phe- 

 nomenon of double refraction in muscles, and to Briicke^s 

 classical memoir, Engelmann states that in spite of proofs 

 being brought forward of the association of other forms of 

 contractile phenomena with the presence of double refraction, 

 e. g. in the muscles of certain infusoria, the results were 

 almost all negative. In consequence, the opinion prevailed 

 that the presence of anisotropous elements in muscle was a 



