68 [May 1, 



Believing that the wide divergence in the conclusions heretofore 

 arrived at has been owing in great measure to difference in the methods 

 of investigation employed, I made many trials in order to find out re- 

 agents which would increase the transparency of the muscular fibres 

 without attacking or at least obscuring the finer fibres of the nerves, 

 and have found the following to be well adapted for the purpose in view. 

 1 . Extremely dilute acetic acid*. 2. Diluted hydrochloric acid in the 

 proportion of 1 part of acid to 1000 of water; but as this reagent 

 eventually softens and destroys the muscles, it is well to observe that 

 the suitable time of exposure to it is from about 12 to 24 hours. 3. 

 Artificial digestive fluid, the use of which for a similar reason requires 

 precaution. 4. Very dilute nitric acid in the proportion of 1 part of 

 acid to 1000 of water. 



The object selected for examination was for the most part the 

 cutaneous pectoral muscle of the frog, in which the ramification of 

 the nerves has been so successfully traced and represented by 

 Reichertf. In general I have found it better not to separate the 

 muscular fibres, although I have not omitted also to examine single 

 fibres from the same muscle, and from the gastrocnemius. The 

 magnifying power employed was from 500 to 600 linear, obtained 

 by Hartnach's lenses "a immersion" No. 9 & 10. I have also tried 

 a power of from 1000 to 1500 as used by Kiihne, but I could discover 

 nothing by its aid which I did not see equally well with the lower 

 amplification. 



In proceeding now to give an account of my own observations, I 

 have first to state that I have been able to confirm the observation 

 of Kiihne that in the frog's muscles the nerve-fibres really branch out 

 at their ends into delicate pale filaments a fact not hitherto recog- 

 nized by Wagner, Reichert and others, who have investigated the 

 relation of the nerves to the muscles in that animal. 



But whilst agreeing with Kiihne as to the existence of these pale 

 fibres, I am satisfied that they are situated, not within the muscular 

 fibre but on its surface, as I shall more fully explain hereafter ; and 

 that they lie outside the sarcolemma, through which they do not 

 penetrate. As to their nature, Kiihne regards them as prolongations 



* I find the best proportion to be from 8 to 16 drops of concentrated acetic 

 acid, sp. gr. 1'045, to 100 cubic centimetres (3^ ounces) of distilled water. 

 t MUller's Archiv, 1851. 



