CENTRAL CONTROL OF THE BLADDER 1 209 



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INTRAVESICAL VOLUME IN C,C. 



FIO. I. Schematic cystometrogiams. .1/ indicates peak 

 pressure during micturition contraction. Segment /, or the 

 initial rise, is segment from zero to first point of inflection. 

 Segment II, or the tonus limb, begins at the first inflection point 

 and either ends at micturition contraction or, in the absence of 

 micturition reflex, continues into Segment III, the ascending 

 limb. [From Tang & Ruch (32).] 



or class of things, and to modify tliein by specific 

 terms to denote more restricted meanings, e.g. 'ac- 

 tive,' 'neurogenic' (Thus may be avoided the no- 

 menclatural impasse reached by physiologists in 

 respect to 'inhibition.') Also, in an area in which 

 quasivitalistic thinking has occurred, it seems best to 

 use an operational definition. Thus, 'tonus' of the 

 bladder is defined simply by the pressure-volume 

 curve yielded by a cystometer. 



Cystometrogram 



Figure i shows a diagrammatic cystometrogram 

 and introduces a terminology, which is without prej- 

 udice in respect to cause, for the various phases of 

 the record. Although the zero pressure on the ma- 

 nometer is set at the level of the symphysis pubis, 

 most cystometrograms show a definite rise in intra- 

 vesical pressure with the first increment of volume 

 (Segment I). The reason for this has not been ex- 

 plicitly stated. After a definite inflection, the AP/AV 

 rises slowly, usually along a slightly positively ac- 

 celerated curve — Segment II, or the 'tonus limb.' 

 Normally, this limb is truncated by the occurrence 

 of micturition, indicated by the arrow labelled M, 

 the maximum pressure developed (semi-isotonic) 

 being indicated by the dot. If micturition does not 

 occur. Segment II continues, the curve 'accelerating' 



FIG. 2. Cystometer used by Mosso and Pollacani who were 

 the first to record cystometrograms. [From Mosso & Pellacani 



(22).] 



more rapidly until it climbs quite steeply. The quasi- 

 inflection, although often sharp, is greatly exag- 

 gerated in the diagram. This ascending limb is 

 designated Segment III to provide for the possi- 

 bility that an additional component of the bladder 

 wall is involved. It is noteworthy that micturition 

 usually occurs before or at this point of inflection, if 

 it occurs at all. 



Mosso & Pellacani (22), who first determined the 

 pressure-volume curve of the bladder using the cys- 

 tometer shown in figure 2, and tho.se who have 

 followed them have been preoccupied with the flat- 

 ness of Segment II and ha\e endowed the bladder 

 with a property of 'adaptation'; or 'accommoda- 

 tion.'- Several authors (8, 9, 19), perhaps following 

 Sherrington, have likened the bladder's reaction to 



° These terms are unlbrtunate because they hint at an active 

 tonic detrusor process, and both ha\'e other technical meanings 

 in neurophysiology. In a recent clinical work, Segment II is 

 attributed to a stretch reflex, although a stretch reflex, did it 

 exist, would cause the pressure to rise, the reverse of accommo- 

 dation. 



