THE ESSENTIALS OF HISTOLOGY. 



by the breaking across of muscle-fibres, the surfaces of the disks show a 

 network with polyhedral meshes in some insects, one formed of lines 



FlG. 85. POKTION OP LEG-MUSCLE 

 OF INSECT TREATED WITH DILUTE 

 ACID. 



S, sarcolemma ; D, dot-like enlarge- 

 ment of sarcoplasm ; K, Krause's 

 membrane. The sarcous elements 

 FIG. 84. LIVING MUSCLE OF WATER-BEETLE (DY- are swollen and dissolved by the 



TISCUS MARGINALIS). (Highly magnified. ) action of the acid. 



s, sarcolemma ; a, dim stripe ; 6, bright stripe ; c, row of 

 dots in bright stripe, which seem to be the enlarged 

 ends of rod-shaped particles, d, but are really expan- 

 sions of the interstitial sarcoplasm. 



radiating from the centre of the fibre in others. The nuclei, with some 

 inclosing protoplasm, usually lie in the middle of the fibre. 



FIG. 86. TRANSVERSE SECTIONS OF INSECT LEG-MUSCLE, VIEWED IN ISOLATED DISKS, 



TREATED WITH DILUTE ACID. 



A, from a beetle. The disk is viewed partly on the flat, partly in profile ; the sarcoplasm 



appears longitudinally as lines, transversely as a network. 



B, from a wasp, showing a radial disposition of the sarcoplasm. 



Wing- muscles of insects. The wing-muscles of insects are easily 

 broken up into sarcostyles, which also show alternate dark and light 

 strise. 



The sarcostyles are subdivided at regular intervals by transverse 

 membranes into successive portions, which may be termed sarcomeres. 

 Each sarcomere is occupied by a portion of the dark stria of the whole 

 fibre (sarcous element) : the sarcous element is really double, and in the 

 stretched fibre separates into two at the line of Hensen (figs. 87, D ; 



