1865.] Distribution of Nerves to Involuntary Muscle. 235 



2. Secondary movements the consequence of vital movements, or of 

 other phenomena, affecting matter which is not in a living state : 



a. Ciliary movements. Probably due to alterations in the quantity of 



fluid within the cell, the changes in the proportion of fluid being 

 brought about by the action of the living or germinal matter in the 

 cell. 



b. Movements of solid particles suspended in fluid in cells, caused by 



currents in the fluid, as the pigmentary matter in the pigment- 

 cells of the frog. Due to the motion of the fluid as it passes into or 

 out of the cell through its permeable wall, this movement being 

 dependent upon changes taking place external to the cell. 



c. Molecular movements. Which affect all insoluble particles, in a very 



minute state of division when suspended in a fluid not viscid. 



d. Muscular movements. Due to a disturbance (electrical or otherwise) 



in the neighbourhood of a contractile tissue that is, a structure so 

 disposed that its constituent particles are susceptible of certain tem- 

 porary alterations in position, which alterations take place in certain 

 definite directions only. 



DISTRIBUTION OF NERVES TO INVOLUNTARY MUSCLE. 



Distribution of nerves to the muscular fibres and other tissues in the 

 bladder of the frog. 



The demonstration of the ultimate arrangement of the most minute 

 nerve-fibres is a matter of such great difficulty that the anatomist is com- 

 pelled to search with the utmost care for a texture the natural structure 

 of which happens to be favourable for his investigation. There are very 

 few textures which possess so many advantages as the bladder of the frog. 

 It is so thin and transparent, that it may be regarded as a natural dissec- 

 tion and thinning-out of some of the most delicate tissues. The unstriped 

 muscular fibres of this organ are extremely fine, and are slightly sepa- 

 rated from one another. Nerve-fibres can often be seen in the intervals 

 between the fibres. 



I have therefore selected this for illustrating the ultimate ramification 

 of the nerve-fibres in involuntary muscle ; but I believe the statements 

 which I shall make will be found to apply with equal force to every variety 

 of this particular form of muscular tissue. 



With regard to the presence of nerve-fibres in involuntary muscle, I may 

 remark that nerve-fibres have been demonstrated in so many different cases, 

 that it is more in accordance with the positive knowledge already gained to 

 infer that they exist in relation with every form of contractile tissue, 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*. 



* By contractile tissue I mean a tissue in which simple movements like shortening and 

 lengthening alternate with one another, each movement heing a mere repetition of the 

 first movement that occurred when ihc formation of the contractile tissue was complete. 



VOL. XIV. T 



