THE DIAGNOSTIC AND PROGNOSTIC VALUE OF BREATH-HOLDING TEST.

This seems an almost absurd question, and yet cumulative experience is showing that the breathholding capacity and the apneic pause can be made of the most practical diagnostic and prognostic value in the routine practice of medicine. In simplicity, scope and utility, respiratory tests may be classified with the taking of the temperature, pulse, and respiratory rates. It is nearly two centuries since Valsalva's classical experiment, in 1740, showed the marked and easily recognizable effect of sustained forced expiration on the pulse beat, and therefore on cardiac efficiency, when the respiratory passages are forcibly closed. A hundred years later, in 1838, Johannes Mueller of Berlin added the comple-