DEFINITION OF CLASS OF CASES UNDER INVESTIGATION For an indefinite time the medical profession has been confronted with a very common and perplexing class of cases, mostly in women, but occasionally in men, in which persistent backache is the chief subjective symptom. These cases present the following symptomatic picture: The pain, generally dull in character, is as a rule referred to the sacral or lumbar region and is frequently felt in one or both sacro-iliac joints; rarely it is complained of in the dorsal region. It also frequently shoots down one or both legs, in which case it is generally classed as "sciatica" and is aggravated by forward bending or flexion of the thigh with the knee extended. The pain in the back and leg are aggravated by standing, and especially by prolonged standing, such as is involved in the fitting of women's