192 THE TISSUE OF THE ORGANIC MUSCLES, BY J. ARNOLD. 



STRUCTURE OF THE NUCLEUS. In perfectly fresh mus- 

 cular fibres treated with serum the nucleus may indeed be 

 perceived, but its contour is not very well defined ; on the 

 addition, however, either of chromic acid (O'Ol per cent.), acetic 

 acid (1 per cent.), or solution of chloride of gold (Ol per cent.), 

 the contours become sharp and dark, whilst the previously 

 homogeneous contents appear finely granular. In the substance 

 of many nuclei, especially when treated with serum and chloride 

 of gold, but less distinctly with acetic acid, there may be 

 observed from two to four large (from O'OOl 0*002 millimeters) 

 highly refractile round granules (fig. 31, a). If one only be 

 present, it lies near the centre, or frequently somewhat nearer 

 to one of the poles of the nucleus. If, on the other hand, two 

 are present, they are situated at the two ends of the nucleus. 

 These granules are most distinct in transverse sections of the 

 nucleus, and are then seldom absent. They may also be per- 

 ceived in association with isolated nuclei, and in such cases they 

 either lie close to the surface of the latter, or project more or 

 less from its margin. 



Frankenhauser* has paid particular attention to the structure of 

 the nucleus ; and although Hesslingi had previously noted the exist- 

 ence of a nucleolus in the interior of the nucleus, Frankenhauser 

 first stated that it was an essential and a never-failing constituent. 

 Piso-BormeJ also observed the presence of nucleoli. 



CONNECTION AND ARRANGEMENT. The contractile fibre cells 

 are united into fasciculi or membranes of various size, through 

 the intervention of a connecting material. The fibres are 

 so arranged that the ends of two or more are inserted 

 between the diverging extremities of two which touch at their 

 dilated middle portion, an arrangement by which an intimate 

 union of the several structures is effected. In cases where the 

 greater number of the fibres are superimposed by their flat sur- 

 faces, a membrane is formed, consisting of one or many layers, 

 the fibres for the most part preserving the same direction in 



* Loc. cit. 



f Gewebekhre, 1866. 



J Molescbott's Untersucliungen, Band ix., 1860. 



