58 THE INVOL UNTAR Y NER VO US S YSTEM 



the 9th and loth nerve roots representing the sacral outflow, 

 does not appear to me to be based on evidence so strong as to 

 overthrow the evidence of other animals. It is true enough that 

 we must attribute a double nerve supply to the frog's bladder 

 corresponding to that of other animals, for adrenalin causes a con- 

 traction of the whole bladder, but this only makes one wonder 

 whether it is right to describe the frog's bladder as purely cloacal. 

 Although the two ductus deferentes (ureters) open into the dorsal 

 wall of the cloaca opposite the bladder orifice and not into the 

 bladder, yet the bladder always contains pure urine unmixed with 

 faeces. The mechanism by which this end is attained is thus 

 described by Gaupp ; by the action of sphincter muscles on the 

 main cloacal tube above and below the orifice of the bladder, a 

 urinary chamber is formed into which the ureters open and thus 

 fill the bladder with pure urine ; further, seeing that the urine 

 is discharged from the bladder clear as water, it follows that nor- 

 mally the sphincter between the rectum and the bladder is kept 

 closed, and the fasces are held back at the lower end of the rec- 

 tum, which arrangement in fact functionally corresponds to the 

 internal sphincter ani of the higher vertebrates. With such an 

 arrangement it is perfectly possible that muscles belonging to the 

 sympathetic system may have spread over the bladder and that 

 the bladder musculature may not belong exclusively to the purely 

 cloacal muscles. Again Kalischer has come to the conclusion 

 that this trigonal musculature is different from the musculature 

 -of the main body of the bladder, "being characterized by the 

 closeness of its constituent fibres and thus differentiated from the 

 coarser muscular tissue of the bladder proper". It is on the 

 contrary of the same kind as that of the urethra and ureters. 



The morphological separateness of this vesicular sympathetic 

 ^musculature from the vesicular cloacal musculature, is further 

 shown by the phenomenon called by Langley and Anderson 

 the " axon reflex ". It was found by Sokownin that, when the 

 inferior mesenteric ganglia were isolated from the central nervous 

 system by the division of the nerve fibres on the abdominal aorta 

 and of the lumbar splanchnic nerves on both sides, then, if the 

 hypogastric on one side was cut and that end stimulated which is 

 connected with the inferior mesenteric ganglion, contraction of the 

 bladder was caused through the medium of the hypogastric nerve 

 of the opposite side ; as though the stimulation of the hypogastric 



