1865.] The Development of Nerve-fibres. 261 



completely covered with nuclei ; and as development advances these nuclei 

 or masses of germinal matter seem to separate further and further from one 

 another, and the delicate nerve-fibres might be said to be drawn out from 

 them. At the same time the muscular fibre increases in size. It will pro- 

 bably be conceded that at an early period of development of a muscle there 

 are masses of germinal matter taking part in the development of the three 

 different structures muscle, nerves, and vessels. Besides these, upon the 

 surface of the muscle, and between the muscular fibres, are masses which 

 have perhaps already given rise to the formation of a soft granular and 

 slightly fibrous connective tissue. I think that these last masses have 

 originated from the same parent masses as the others. Indeed it is certain 

 that this must be so. Of the masses taking part in the development of a 

 bundle of nerve-fibres, those on the surface produce not true nerves, but 

 connective tissue, and so with regard to muscles, vessels, and other textures. 



The part taken by the germinal matter in the development of muscles, 

 nerves, and vessels may be studied in the fully-formed frog, and with 

 greater facility than in the embryo. At certain intervals amongst the 

 large muscular fibres of the frog may be discovered with some difficulty 

 some bundles of finer muscular fibres. These are most distinctly seen, 

 however, in the thin breast- muscle of the frog, where they were discovered 

 by Kolliker. They were termed by him " nerve-tufts," and are figured in 

 his Croonian Lecture, delivered in 1862 (Proceedings of the Royal Society, 

 1862, p. 78). I have had Kolliker' s figure copied. It does not, how- 

 ever, represent all that may be seen in these swellings, prepared according 

 to the particular plan before alluded to (p. 258); for the numerous oval 

 nuclei, figured in Kolliker's drawings, are represented by him as being 

 pretty generally diffused throughout the swelling, and as not being con- 

 nected with one another, or with any definite structure. The relation of 

 the nerve-fibres to these nuclei is not indicated in Kolliker's drawing, nor 

 is the meaning of these numerous nuclei discussed. 



Some of the nuclei (masses of germinal matter), however, are seen in 

 my specimens to be nuclei in the course of very fine nerve-fibres nuclei 

 which take part in the formation of the nerve-fibres themselves. Others 

 are the nuclei of the muscular fibres which are undergoing development, 

 and over the surface of which the fine nerve-fibres are spread out. These 

 facts are demonstrated in several specimens which I have mounted in strong 

 glycerine and acetic-acid syrup*. A portion of one of these is represented 

 in the figure to which I now point. This drawing, which is magnified 700 

 diameters, appears somewhat confused, owing to the very close proximity 

 of the nerves to the muscles. It is, however, a careful copy of one of my 

 specimens just at the spot where three dark-bordered nerve-fibres pass into, 

 or emerge from, one of the " nerve-tufts." In this drawing I have shown 

 one branch of a dark-bordered nerve-fibre and its division into two very fine 



* " I have found this strong acetic-acid syrup a most valuable agent in these and kindred 

 investigations." How to Work with the Microscope, third edition, p. 202. 



