472 PHYSIOLOGY CHAP. 



the corresponding motor nerves to the bladder, (c) In the trans- 

 mission of excitation from the sensory sympathetic nerves to the 

 motor nerves of the bladder, the inferior mesenteric ganglion acts 

 as the reflex centre. 



All these investigations concern the innervation of the 

 detrusor muscle exclusively, because they were carried out by the 

 introduction into the bladder of a cannula or catheter connected 

 with a water manometer, which threw the sphincter of the bladder 

 out of play. Further, the motor nerves to the bladder were almost 

 always stimulated reflexly, from the central end of the divided 

 sensory nerves. The effects on the detrusor and sphincter of direct 

 excitation of the motor paths to the bladder had next to be 

 studied, to see if they are identical or antagonistic, in accordance 

 with the function of the two muscles. 



This most important problem was ingeniously solved by von 

 Zeissl (1893). He confined his experiments on curarised dogs to 

 studying the effects of excitation of the hypogastric nerves and 

 the nervi erigentes on the detrusor and on the sphincter. With 

 this object he employed a method similar to that which Eehfisch 

 subsequently modified so as to render it applicable to man (see 

 Fig. 128, p. 467). After laying open the peritoneum, he tied one 

 ureter, and connected the other with a pressure-bottle by means 

 of which the bladder could be filled. He then interrupted the 

 communication of the bladder with the bottle and brought it into 

 relation with a mercury manometer, which recorded variations in 

 tone (contraction or expansion) of the detrusor on a revolving 

 cylinder. Lastly, he tied a tube into the urethra, and connected 

 it with a plethysmograph, by which the amount of flow from, the 

 bladder is recorded on the drum. On comparing the two curves 

 obtained from stimulation of the hypogastric or the erector nerve, 

 the action of these nerves on the two antagonistic muscles of the 

 bladder can be computed. 



The following conclusions appear from von Zeissl's work : 



(a) The nervus erigens contains motor fibres to the detrusor 

 and inhibitory fibres to the sphincter, because its peripheral 

 stimulation causes contraction of the former, and expansion 

 (relaxation) of the latter. (6) The first effect is quite independent 

 of the second, since it always precedes it by a greater or less interval, 

 so that the escape of fluid from the bladder cannot be regarded as 

 a direct effect of vesical contraction, (c) If the contraction of the 

 detrusor is hindered by substituting a glass bell-jar for the wall 

 of the bladder, stimulation of the nervus erigens only produces 

 dilatation of the sphincter, showing that this effect is not passive, 

 but depends on specific inhibitory or diastolic fibres contained in 

 the excited nerve, (d*) The hypogastric nerves contain motor 

 fibres to the sphincter, and moderator nerves to the detrusor, since 

 their peripheral stimulation arrests the continuous flow of urine 



