Orchidometer

thumb|300px|A schematic of an orchidometer An orchidometer (or orchiometer) is a medical instrument used to measure the volume of the testicles.

==Instrument== right|thumb|178x178px|Tanner scale for males with corresponding orchidometer bead and volume. The orchidometer was introduced in 1966 by Swiss pediatric endocrinologist Andrea Prader of the University of Zurich. It consists of a string of twelve numbered wooden or plastic beads of increasing size from about 1 to 25 millilitres. Doctors sometimes informally refer to them as "Prader's balls", "the medical worry beads", or the "endocrine rosary".