Larva of Ephemera marginata, magnified. The central shaded line represents the great 

 dorsal channel of the blood. The lateral branched lines the tracheae. 



CHAPTER III. 



ON THE INTERNAL ANATOMY OF INSECTS. 



OF THE Muscles of Insects. Muscle is a substance which 

 yields to the touch : it consists of two parts ; the body of 

 the muscle, which is fleshy ; and the extremities and coat- 

 ing of the muscle, which are tough, strong, and elastic, 

 and are designated as tendon. The surface of muscle is 

 a beautiful microscopic object : it presents a series of 

 exceedingly fine transverse lines, which, in contraction, 

 assume an undulated form. The fibre of muscle is much 



