166 METHODS OF MICROSCOPICAL RESEARCH. 



in dimensions, and shadow, in different lines, this 

 abstract knowledge is important, and should be 

 acquired, as many objects could not be effectively 

 represented without its study always keeping to 

 general appearances ; it is an ability which removes 

 difficulty in unravelling the disposition of parts, 

 especially under high powers ; when sections are 

 cut either too thin, slightly oblique, or disrupted 

 by the knife, the mechanical interferences of parts, 

 when understood, may be restored. The functions 

 of an artist, cognisant of a condition of antecedents 

 may be fairly exercised in the progress of a draw- 

 ing, but it must never trench upon absolute truth 

 and discrimination in treatment a drawing may 

 be ruined in a moment by a false line involving 

 impossibility of structure ; to a critical eye, this 

 is fatal. In fine work, dealing with malpositions, 

 shrinkage of tissues, disseverances and pseudo- 

 appearances inevitable even in the finest prepara- 

 tionsthe utmost judgment is required. 



The effect of a microscopical drawing is enhanced 

 by its inclusion in a circle surrounded by a black 

 margin forming a square. The size of the circle 

 is important it may be too large, or too small ; 

 experiment proves that a space three inches and 

 three-quarters in diameter approximates nearest to 

 the impression made on the mind of a " field " as 

 seen with a B eye-piece ; this circle may encompass 

 magnifications under any power. A metal plate 

 four inches and three-quarters square, with an 

 opening of the dimensions given, should be pro- 

 cured, this ascertained gauge will soon prove a 

 necessity ; placed on a drawing block, a pencil 

 swept round the circle and outside the square gives 



