136 ELEMENTARY lUOLOGV. [CHAP. 



the dark). Finally tear uj) with a coui)le of 

 needles in glycerine. 



tt. Longitndi)ial striae; parallel lines, differentiated 

 under the above treatment, which can he 

 traced throughout the entire length of the 

 fibre, traversing clear and dark zones aHke. 



/i. 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 hematoxylin, 

 imbed and cut transverse sections. Mount in 

 Canada balsam and examine with a low power. 



a. The nen'e inink; composed of an immense 

 number of small rounded iicrve fibres. 



p. The perineurium ; a deeply staining sheath, 

 seen to carry blood-vessels (cf. perimysium and 

 periosteum). It may be in part fat laden. 



y. The nen'e bundles: lesser divisions of the trunk, 

 each bound up in an ingrowth of the perineu- 

 rium (cf. muscle bundles). 



A Examine the thinnest portion of a nerve bundle 



under a high power ; it will be found to contain — 



a. Medullated 7ier%'e fibres ; in section round, each 



witli a central deep-stained portion {ciAis fibre) 



