Applications of Electronics in Medicine 51 



ing the heart sounds on gramophone records. Sound can be 

 recorded on discs, steel wire, and photographic film. It may also 

 be recorded by embossing a track with a needle on film or plain 

 cellophane strip. 



Reynolds '^^ has experimented on the problem of synchronizing 

 the electrocardiogram, as recorded by a cathode-ray type electro- 

 cardiograph, with a cinematographic film of the heart cycle. 

 The writer suggests that, theoretically, it should be possible to 

 develop this technique so that a cinematographic film of the 

 cardiac cycle could be produced, which has a sound track of 

 the heart sounds. If necessary, a simultaneous jugular sphygmo- 

 gram, phonocardiogram, etc., could also be shown on the film. 



Synthetic sound is a term applied to sound produced by 

 methods like those devised by Rudolf Pfenniger who painted 

 by hand the desired wave forms, afterwards photographing 

 them onto a sound track for conversion into sound. 



Electronic pH Meters 



The estimation of the hydrogen-ion concentration of fluids 

 such as the blood in clinical practice is, in the main, confined 

 to the tintometer method. A number of pathological depart- 

 ments and bacteriological research institutions are now using pH 

 meters employing thermionic-valve circuits. The results ob- 

 tained with these devices are more accurate than those obtained 

 with other methods. Serum electrodes have been devised which 

 are capable of dealing with very small quantities of fluid — 

 0.2-0.3 milliliters. In clinical bacteriology, the growth of cul- 

 tures can be retarded, advanced, or even the manner of growth 

 can be directed by proper pH control. 



Thermostromuhr Apparatus 



Rein ^^ introduced the thermostromuhr method for measuring 

 blood flow through a blood vessel. A small insulator clip is 

 placed around the blood vessel. Two small plates which pass a 

 radio-frequency current through the blood stream are fixed in 



