110 , FRANCIS DARWIN. 



from the ganglia situated between the mucous and muscular 

 coats of the intestine to capillary vessels. Dr. Klein sug- 

 gested that the relations of ganglia to blood-vessels might be 

 conveniently studied in the rabbit's bladder, where he has 

 already pointed out the existence of numerous sympathetic 

 ganglia (' Handbook for the Physiological Laboratory/ p. 73). 

 The ganglia are found in considerable numbers in the bladder 

 of this animal, but are more especially numerous in that of 

 the dog. In the rabbit's bladder they are found most 

 abundantly on the thickened lateral edges of the organ, along 

 which the main blood-vessels also take their course ; in the 

 dog they are more numerous on the posterior than on the 

 anterior surface of the bladder. 



The method employed was that recommended by Dr. Klein 

 (loc. cit.), viz. " bits of the fresh bladder are coloured with 

 chloride of gold, and then steeped in acidulated water until 

 they swell out into a gelatinous translucent mass, then mem- 

 branous fragments stripped off with the forceps, or snipped 

 off with the scissors, are spread out and covered in glycerin." 

 I found it best to keep the bladder intact until after it had been 

 treated with the acidulated water ; if it is cut in half, the two 

 pieces turn inside out as they swell up, and it is then very 

 much more difficult to snip off thin strips from the external 

 surface. The fragments should be placed on the glass slide 

 with their external surface downwards. 



The ganglia are situated in the external coat of the bladder, 

 and are of such a size that many of them, in the dog's bladder 

 at least, can be seen with the naked eye. Fig. 1 represents 

 the posterior surface of the bladder of a young puppy, as seen 

 with a very low power. It shows the general arrangement 

 of the ganglia and the manner in which they are connected 

 with each other by nerve-trunks ; it will be noticed that they 

 form chain-like plexuses running with the principal blood- 

 vessels of the bladder; a chain of minute ganglia may also 

 be remarked running partly round the base of the bladder. 



The ganglia are of various sizes : the largest one observed 

 has a long diameter of 0*9 mm., and a transverse one of 

 0'12 ; one of the small ganglia is 0*09 mm. in length by 

 0045 mm. in breadth. They present considerable variety in 

 their shapes and have irregular outlines, which may be 

 roughly circular, oval, or polygonal. The nerve- trunks with 

 which they are connected are made up of non-medullated 

 nerve-fibres, with a few medullated fibres appearing oc- 

 casionally. The ganglia are either situated at the points of 

 intersection of several nerve-trunks or they are found seated 

 on single trunks. In the former case the groundwork of the 



