DISTRIBUTION OF NERVES, ETC., IN BLADDER OF FROG. 237 



positive knowledge already gained to infer that they 

 exist in relation with every form of this texture, even 

 in cases in which we may still fail to demonstrate 

 them, than to infer they are absent simply because 

 we have failed to render them distinct. And as I 

 have detected nerves in every form of contractile 

 tissue that I have examined, I think it right to con- 

 clude that contractile textures are invariably asso- 

 ciated with nerves.* 



The bundles of dark-bordered fibres which may be 

 traced to the posterior part of the frog's bladder 

 divide and subdivide freely, spreading out in the 

 form of a lax network. The fibres may be followed 

 for some distance, and many may be traced to their 

 ultimate distribution in the thin tissue of the bladder. 

 Over a great part of the frog's bladder, however, no 

 dark-bordered fibres or bundles of moderately coarse 

 fibres can be detected ; yet the organ is in every part 

 very freely supplied with nerves. 



Bundles of excessively fine fibres, first described 

 by me,f may be traced running parallel with many 

 of the small arteries, and may be seen to divide and 

 subdivide into finer bundles, which at length form a 

 plexiform network. Here and there is seen a plexus 

 composed of multitudes of very fine fibres, from 

 which small bundles of fine fibres diverge in different 

 directions. That very many of these fine fibres come 

 from the numerous ganglion-cells found in connexion 

 with the nerve- trunks there is no doubt ; and it is 

 equally certain that many also result from the divi- 



* By contractile tissue I mean a tissue in which simple 

 movements like shortening and lengthening alternate with one 

 another, each movement being a mere repetition of the first 

 movement that occurred when the formation of the contractile 

 tissue was complete. See page 214. 



f "On very fine Nerve-fibres in Fibrous Tissues, and on 

 Trunks composed of very fine Fibres alone." (Archives of 

 Medicine, vol. iv.) See also paper in Phil. Trans., June, 1862. 



