516 



resolved into sarcous elements of great distinctness and beauty, while 

 new and similar fibrillse are developed along its sides in the way 

 already explained. The subsequent series of changes do not diifer 

 materially from those that occur in the inferior classes. 



It is evident that this description of the development of muscular 

 fibre is entirely opposed to the cellular theory of Schwann ; while it 

 agrees in some points with that of Lebert (Annales des Scien. Nat. 

 1849-50), but more with that of Savory (Phil. Trans. 1855). In no 

 instance have I found that nucleated cells, properly so called, are 

 concerned in the office of development ; for the finely granular blas- 

 tema attached to the nuclei, although it frequently assumes the shape 

 of a fusiform cell, is not invested with a cell-wall, in the proper sense 

 of the word. Such an envelope, however, is sometimes simulated by 

 the investing sarcous substance or fine lateral fibrillse when they are 

 first laid down on the sides of the fusiform mass and meet each other 

 at each extremity to form a single fibre or process. Indeed, according 

 to my own observations, as already remarked, this is precisely the 

 mode in which the organic muscular-fibre-cell is developed ; so that 

 the striped muscular fibre, instead of being the product of nucleated 

 cells, would appear to be itself, at first, an instance or mode of cell- 

 formation, which finds its prototype in the organic muscular fibre- 

 cell, and in which the cdl-waU is substituted and represented by the 

 investing sarcous substance. 



II. "On the Influence of Temperature on the Electric Con- 

 ducting Power of the Metals." By A. MATTHIESSEN, Esq., 

 P.E.S., and M. VON BOSE. Received December 5, 1861. 



(Abstract.) 



In the first part of the paper we have described the apparatus used 

 for the experiments, together with the precautions taken to ensure 

 correct results ; in the second we have given the results obtained with 

 the pure metals silver, copper, gold, zinc, tin, arsenic, antimony, 

 bismuth, mercury and the metalloid tellurium. The conducting 

 power of the wires, or bars of each, was determined at about 12, 25, 

 40, 55, 70, 85, and 100 C. ; and from the mean of the eight ob- 

 servations made with each wire (four at each temperature on heating, 



