FOREWORD TO PART I 



9 



form of thin cell, which may be either of 

 cement or paper, and which servos the 

 additional purpose of preventing the 

 crushing of the object by the coverslip. 

 Most wholemounts are, however, pre- 

 pared in a preservative medium, wliicli 

 may be either aqueous, colloidal, or resin- 

 ous. Many of these whole objects are rela- 

 tively thick so that some method must be 

 adopted of ])roviding space for them under 

 the coversUp. Fig. 2 shows an object 

 mounted in a deep cell of glass, while Fig. 

 3 shows an alternative method in which a 

 relatively thick shde has had an oval 

 cavity ground into it. As will be seen from 

 the figure these mounts are heavily var- 

 nished at the edges to prevent the evap- 



oration of fluid or the A\ithdrawal of water 

 from the colloidal medium. Wholemounts 

 prepared with | 'resinous media, w'hich 

 harden and thus hold the coverslip in 

 place, are frequently not varnished at the 

 edges though some case can be made out 

 (Gray 193G, Microsc. Rec, 38) for the ap- 

 phcation of a ring of varnish around the 

 edge of balsam mounts. 



Smear preparations (Fig. 4) are almost 

 invarialily prepared in resinous media and 

 equally invariably the edges of the covcr- 

 shps are not varnished. Sections (Figs. 5 

 and 6), either single or serial, are univer- 

 sally mounted in resinous media and the 

 edges of the covershp are practically never 

 varnished. 



