RELA TION OF TISSUES. 



253 



structures which are combined to form the true skin of the 

 frog. The capillary vessels have been injected with 

 Prussian blue fluid. The bioplasm of all the textures 

 represented in the drawings has been stained with carmine. 

 In fig. i, the nerves are not represented, but in fig. 2, the 

 vessels, nerves, pigment cells, and the bioplasm of these 

 tissues are all seen. The connective tissue itself has been 

 omitted in the drawing, in order that more important 

 textures should appear clear and distinct. The nerves, 

 vessels, and pigment cells are separate from one another. 

 Although they are in very close proximity, they are in no 

 case blended together. Each performs its special office, 

 but all are essential and necessary to the proper action of 

 the composite texture. They are developed together. As 

 soon as they are formed they begin to act, and the action 

 continues while formation still goes on. The actions of the 

 several tissues are harmonised. 



Now, it is important that the reader should know that 

 no one has succeeded in showing how these several tissues 

 become mutually adapted to one another and interdigitate 

 as it were during the progress of growth. 



Notwithstanding the positive assertions that have been 

 made concerning the formation and action of the highest 

 and most complex tissues of man, it is a fact that no one 

 has yet adequately explained how the intricate arrangement 

 of the nerve fibres is brought about in the skin even of the 

 frog. The nerve threads are intertwined and interlace with 

 one another in a marvellous manner. Most important 

 ends are served by this arrangement, which, it need hardly 

 be said, cannot be accounted for by attractions and repul- 

 sions, or imitated artificially. Everyone will admit that it 



