Connective Tissue, Nerve, and Muscle. 5.27 



tendon. Longitudinally the fibre is seen to consist of parallel bundles 

 of uniform width, separated by spaces that are indicated by distinct lines ; 

 and, distributed at intervals in the lines, are oblong nuclei, the long axis 

 of which is parallel to that of the fibre. The breadth of the bundles is 

 about the same as that of a secondary bundle in tendon ; their surface 

 is smooth and homogeneous (figure 25, Plate XI.). 



A transverse view, corresponding to that of a cross section of tendon, 

 shows the muscular substance intersected by stellate spaces, in some of 

 which nuclei are seen, and, branching out from the spaces, a rich anasto- 

 mosing network of fine dark lines divides the substance of the fibre into 

 a number of compartments. Between the appearance I have just described 

 and^that of a cross section of tendon similarly prepared, the only difference 

 is that, in muscle, the fields enclosed by the dark lines are dotted over by 

 minute points, which may indicate the fibrillae. 



Nuclei are always seen in fibres successfully stained with gold, and 

 especially when the fibre is separated by teasing into the bundles of 

 fibrillse ; but their number is much less than that seen when haematoxylin 

 is used. "We have seen how, in the cornea, gold when it has deeply stained 

 the nucleus of the branched cells leaves that of the flat cell invisible, 

 while haematoxylin colours them. both. So it is generally in the capil- 

 laries of blood-vessels. I have found that, in the capillaries of the muscles 

 of the frog, these invariably consist of two layers an internal epithelial 

 layer, the outlines of whose cells are defined by nitrate of silver, and an 

 external layer, into which a fine system of branched cells enters. Hsema- 

 toxylin brings out the nuclei of the cells of both layers. The deep stain- 

 ing with gold, while it differentiates the layers by staining the internal 

 (epithelial) more intensely than it does the outer (adventitious) layer, shows 

 no nuclei in the epithelium, while the nuclei in the outer layer are well 

 marked. 



In applying to muscular fibre the experience thus acquired, we are 

 warranted in concluding that the nuclei coloured in gold are those of cells 

 that belong to the branched system, and which are the characteristic 

 nuclei seen in the transverse view of a gold-stained muscle, while the 

 great majority of those stained by hgematoxylin belong to the flat cells of 

 the lymphatic system. 



The isolation of these cells is surrounded Ijy difficulties, which are, how- 

 ever, surmountable. In fibres deeply stained by gold I have isolated long 

 thin flat cells, lying amongst the fibrillaB, which are identical in shape 

 with similar cells in the cornea. They were coloured uniformly deep 

 purple, and a distinct nucleus was not visible. They are represented in 

 figure 27, Plate XI. 



Immediately investing the bundles composing a muscular fibre is the 

 sarcolernma, which is externally, as I have shown, covered with flat cells. 

 The property possessed by this membrane of resisting acetic acid is the 

 cause of a characteristic appearance presented by a muscular fibre under 



