THE DETECTION OF DIFFUSION ARTEFACTS 35 



TABLE II 



Time limits of the various steps in the procedure of Takamatsu and 

 Gomori. 



Step in Procedure 

 Steps before incubation 



(a) Fixation 



(b) Dehydration (3 changes) 



(c) Clearing (3 changes of cedarwood 

 oil) 



(d) Infiltration with wax 



(e) Drying of sections on slide at room 

 temperature in desiccator at 

 37° C. in incubator 



(/) Removal of wax in xylol 

 (g) In celloidin or alcohols 

 {h) In distilled water 



Steps after incubation 

 (i) In calcium nitrate 

 (j) In cobalt nitrate 

 (k) In distilled water 

 (0 In ammonium sulfide 

 (m) In tap water 

 (n) In alcohols or xylols 



any tendency towards acidity in these solutions, which would, 

 of course, cause removal of precipitate from the sections. 



Intact paraffin blocks will often keep 12 months or more with- 

 out serious loss of activity. The enzyme in blocks which have 

 been cut often seems to be less stable. 



The Detection of Diffusion Artefacts 



We may classify the artefacts which may arise by diffusion 

 processes into three groups. 



1. Diffusion of calcium phosphate, cobalt phosphate, or cobalt sulfide. 



2. Diffusion of enzyme, enzyme activator, or enzyme inhibitor after 

 fixation. 



3. Diffusion of enzyme, enzyme activator, or enzyme inhibitor during 

 fixation. 



