Described by Ord in 1884 as a simple physical sign in myxedema, the delayed ankle-jerk response has since become an invitation to complex reflex-timing devices. The first ankle-jerk timer was a pneumatic registering system introduced by Chaney in 1924. There soon followed a variety of electronic, photoelectric, and electromagnetic instruments, each with its claim to superior accuracy, portability, and ease of handling.
Despite refinements in measuring tools, not all investigators agree on the value of the reflex-time estimation as a test for hypothyroidism. Rives et al1 question the sensitivity of the test. In their series of hypothyroid patients, the prolongation of the reflex, as measured by the contraction phase, did not prove a reliable guide in diagnosis. On the other hand, Nuttall and Doe,2 taking as their measurement the interval between maximal rate of contraction and that of relaxation (half-relaxation time)—an interval which in their view is a