24 Introduction 



Nicotinamide cannot be synthesized in adequate amounts in the human body 

 and is, therefore, a vitamin indispensable to man. It is less known that nicotin- 

 amide is also a therapeutically effective chemical. Ten years after the discovery of 

 the physiological function of nicotinamide, in 1945, Vital Chorine 3 found that 

 tubercular guinea pigs and leprous rats could be healed by the use of nicotinamide, 

 whereby 0.3 to 1 g per kg of body weight was sufficient to effect a eure. Free 

 nicotinic aeid proved therapeutically ineffective. This action of nicotinamide, a com- 

 pletely nontoxic substance, a component of hydrogen-transferring enzymes, was 

 responsible for the testing of nicotinamide and its isomers and homologs with 

 regard to the effect of these Compounds on human tuberculosis. The result of this 

 work was the discovery by Gerhard Domagk of the action of isonicotinic aeid 

 hydrazide, the most effective remedy against human tuberculosis today. 



II. Manometry 



Complicated manometric equipment, such as was used to measure the quantum 

 requirement of photosynthesis — differential manometers, readings by means of 

 the cathetometer-microscope, the rotary motion of round vessels — was replaced 

 in 1945 by simple manometers, readings with the unaided eye, and the straight- 

 line motion of reetangular vessels (8). The transition in the motion of the mano- 

 metric vessels from circular to rectilinear caused one of the prineipal sources 

 of error in manometry to disappear, i. e., the formation of foam when the vessels 

 are shaken. A cell Suspension, formerly füll of bubbles after being shaken for no 

 more than 1 hour, is today free of bubbles after being shaken for 24 hours. This 

 enabled us to change over to experiments of any desired duration and, thereby, 

 to obtain manometric effects of any desired magnitude — an example of what may 

 be achieved by means of apparently minor modifications in technique. If irradiated 

 manometric vessels moving in a straight line run the risk, at the end of their paths, 

 of moving beyond the beam of light, this can be prevented by the use of mirrors 

 that are attached to and move along with the manometers. 



Metabolism measurements in serum have also become simplified, because the 

 complicated calculation of carbon dioxide retention has been replaced by a simple 

 direct method of determination. 



The introduction of the new "side Chamber" and "trough" vessels, which will 

 completely displace the older types of manometric vessels, represents a decisive 

 advance in manometry (41, 42, 72). Carbonate-bicarbonate mixtures put into the 

 side Chambers maintain constant pressures of carbon dioxide within the entire 

 side-chamber vessels, over the ränge of 0.3 to 600 mm Brodie; cells maintained 

 in their physiological environment in the main compartment of the vessel can 

 thus no longer be damaged by the carbonate mixtures in which they formerly were 

 suspended. This method constitutes the Solution of the oldest problem of biologi- 

 cal manometry: to determine the oxygen metabolism under physiological carbon 

 dioxide pressures by means of one vessel. It obviates the use of the two-vessel 

 method in all cases in which the carbon dioxide is of no interest. The new manome- 

 tric vessels may be obtained from Aminco, Silver Springs, Maryland, USA. 



