136 ELEMENTARY BIOLOGY. [CHAP. 



the dark). Finally tear up with a couple of 

 needles in glycerine. 



a. Longitudinal stria; parallel lines, differentiated 

 under the above treatment, which can be 

 traced throughout the entire length of the 

 fibre, traversing clear and dark zones alike. 



ft. Transverse networks ; seen, in the regions of 

 the septal lines, traversing the fibre at right 

 angles to a and thickened at their points of 

 intersection with the same. When looked 

 at en face they present a honeycomb-like 

 appearance. 



iv. and v. may be profitably repeated upon 

 the muscle fibre of an insect. 



9. Nerve. 



a. Preserve a portion of the iliac nerve in spirit of 

 increasing strengths; stain with haematoxylin, 

 imbed and cut transverse sections. Mount in 

 Canada balsam and examine with a low power. 



a. The nerve trunk; composed of an immense 

 number of small rounded nerve fibres. 



ft. The perineurium ; a deeply staining sheath, 

 seen to carry blood-vessels (cf. perimysium and 

 periosteum). It may be in part fat laden. 



y. The nerve bundles; lesser divisions of the trunk, 

 each bound up in an ingrowth of the perineu- 

 rium (cf. muscle bundles). 



b. Examine the thinnest portion of a nerve bundle 

 under a high power ; it will be found to contain 



a. Medullated nerve fibres ; in section round, each 

 with a central deep-stained portion (axis fibre] 



