THAT POWDERED GLASS IS A SECRET AND 

 DEADLY POISON 



HIS is a very old fallacy. It figures in the 

 "Vulgar Errors" of Sir Thomas Browne and 

 it survives even to this day amongst a certain 

 class of pseudo-scientific writers. Even within 

 two or three years a man was charged with committing 

 murder by means of powdered glass and was tried for a 

 capital offense. Of course the physicians who went on 

 the witness stand scouted the idea of powdered glass 

 acting as a virulent poison and one of them offered to 

 swallow a tablespoonful of the stuff in open court. Sir 

 Thomas Browne experimented with it on dogs and tells 

 us that he gave "unto dogs above a dram thereof sub- 

 tilely powdered in butter and paste, without any visible 

 disturbance." Nevertheless he tells us that "glass grossly 

 or coarsely powdered is mortally noxious, and effectually 

 used by some to destroy mice and rats." 



This idea that powdered glass is an efficient poison for 

 rats and mice is quite prevalent, but it has been proved 

 by recent experiments made under the direction of the 

 United States Department of Agriculture that glass, 

 whether coarsely or finely powdered, has no ill effects 

 upon rats. Rats were fed for some time on food mixed 

 with the glass and they did not seem to be injured by it. 

 And when examined after being killed, the alimentary 

 canal was found to be in normal condition. So that we 

 may safely relegate the belief in powdered glass as a 

 poison to the list of popular fallacies. 



