WITH THE MICROSCOPE. 333 



my opponents are many and powerful, the facts in favour of my 

 own view are now very numerous and almost every new investiga- 

 tion I attempt enables me to add more to the number. My con- 

 clusions rest upon observations made upon many different tissues and 

 organs of vertebrata differing widely from one another, as well as upon 

 those of numerous invertebrate animals. I cannot therefore yield. 

 I consider that numerous specimens I have made fully justify me 

 in maintaining the general proposition that in all cases the terminal 

 distribution of nerves is a plexus, network or a loop, and hence 

 that in connection with every terminal nervous apparatus there must 

 be at least T.AVO fibres, and that in all cases there exist complete circuits 

 into the formation of which central nerve cells, peripheral nerve cells 

 and nerve fibres enter. All these elements are in structural connec- 

 tion with each other. I propose now to illustrate these general 

 observations by one or two examples. 



3O. The Distribution of Motor Serves to Muscles. In pi. LX, 

 fig. 380, the ultimate arrangement of the finest nerve fibres in volun- 

 tary muscle is represented. A full explanation will be found beneath 

 the drawing, so that it is not necessary to enter into a minute de- 

 scription in the text. 



The nerves distributed to the muscular fibres of insects are much 

 finer and more delicate, and far more difficult of investigation than 

 those of vertebrate animals. Many writers have been led into 

 fundamental errors concerning the structure and arrangement of 

 nerve fibres in this class of invertebrata. What really is a compound 

 nerve fibre, composed of very many individual fibres, has been looked 

 upon as a single nerve fibre. The nuclei of the finer nerve fibres have 

 been entirely passed over. Muscular nuclei have been regarded as 

 bodies, in which muscular nerve fibres end. A plexus formed by the 

 compound nerve trunk at the point where it reaches the sarcolemma 

 and it is about to break up and spread over the surface of this 

 membrane, pi. LXI, figs. 381, 383, has been regarded as the terminal 

 portion of a single nerve fibre beneath the sarcolemma and in contact 

 with the muscular tissue." 5 



In plates LXI and LXII, the manner in which very fine nerve 

 fibres are distributed upon the sarcolemma of insect muscle is well 

 seen. The reader should refer to the full explanation under each of 

 the figures from fig. 381 to 387 inclusive. See also paper on the 

 "Structure of the Sarcolemma of Insects," &c., Microscopical Journal 

 for July, 1864. 



The arrangement of the ultimate nerve fibres in involuntary or 



* Upon this subject see 'Controversy' Archives, vol. IV, p. 161, and a paper by 

 Mr. Gedge, of Cambridge, in the July number of the Microscopical Journal, 1867. 



