ON THE STRUCTURE OP MUSCULAR FIBRE. 255 



that it was formed by a number of narrow parallel cylindrical 

 bands corresponding to what I had designated a primary 

 bundle and to Kolliker's Muskel-sdulchen. I shall continue in 

 this paper to use in reference to them the term primary 

 bundle. When a secondary bundle was teased a primary 

 bundle could occasionally be isolated to a considerable length, 

 and the only reason why there was any difficulty in isolating 

 them Avas the size of the points of the needles as compared 

 with the narrowness of the structures which had to be mani- 

 pulated. There was no other than the mechanical difficulty 

 of manipulation to prevent every muscular fibre being com- 

 pletely separated into isolated primary bundles, and with 

 fine needles, a good dissecting lens and sufficient patience, 

 this would have been possible. I will return to what 1 

 believe to be the cause of this extraordinary change in the 

 physical qualities of the fibres, but will first describe the 

 histological characters of the difierent elements which were 

 thus made available for study. 



In the undivided fibre an indication of the secondary bundles 

 could be detected where it was flattened, and the primary 

 bundles were indicated by an arrangement of nuclei in 

 parallel lines, the number of nuclei visible being enormous. In 

 fig. 10 a fibre is shown as seen by a low power (No. 3 Obj. 

 of Hartnack) ; at one end the fibre is seen unbroken, whilst 

 at the other it is seen broken up into three parts. Fig. 11 

 shows more highly magnified the divided end of the same 

 fibre and the nuclei with which it is filled. In order to 

 give a still clearer idea of the number of nuclei fig. 12 has 

 been added. 



Since the primary bundles could also be separated from 

 each other the objection might fairly be taken to the secon- 

 dary bundles that they represent parts of the fibre separated 

 fortuitously, and in some instances this may have been the case. 

 But against this view as applicable to all the so-called secon- 

 dary bundles is the uniform ease with which a fibre could 

 always be separated into several parts of fairly equal size, 

 and the fact of the indubitable arrangement of the mus- 

 cular fibres of the frog in secondary bundles which I had 

 shovpn by the action of chloride of gold. (See the * Proc. 

 Roy. Sec.,' No. 155, 1874; Plate XI, figs. 26 and 28.) 



In the preparations I am now considering the most im- 

 portant individual element is the primary bundle. The 

 secondary bundles and the fibre itself are simply collected 

 groups of these. By no previous method of preparation has 

 this important element been so completely brought within the 

 scope of observation. 



