The Bristol stool form scale or BSF-Scale is a diagnostic aid to classify the human stool form into seven distinct groups. It was developed by researchers1 at the Bristol Royal Infirmary2 in the 1980's as what has been described as a "user-friendly" scale.
The Bristol stool form scale in full:-
Apparently "the ideal stools are types 3 and 4, especially type 4, as they are most likely to glide out without any fuss whatsoever"3. Types 1 and 2 are indicate of constipation and types 5 and 6 of diarrhea.
The BSF-Scale is in common use by the medical profession in the United Kingdom but how widespread is its adoption throughout the rest of the world I do not know.
The British are in no way obsessed by the subject of bowel movements
NOTES AND SOURCES
1 The nature of the research conducted I leave to your imagination.
2 The Bristol Royal Infirmary commonly known as the 'BRI', a hospital in Bristol, England.
3 See Family Doctor Publications in association with the British Medical Association at
http://www.familydoctor.co.uk/htdocs/BOWELS/BOWELS_specimen.html
4 Other sources consulted;
http://www.malehealth.co.uk/keyinfo/bowelstools.htm
http://www.bowelcontrol.org.uk/index.html