18 HISTOLOGY 



10. Sciatic Nerve. Cut out a quarter of an inch of the sciatic nerve of the frog. Hold one end on a slide 

 by the blunt edge of a scalpel. Quickly tease out with a needle the other end into a fan. Add normal salt 

 solution and put on a coverslip. Observe the nerve fibres, which are of double contour on account of their fatty 

 sheath. At ends observe the transparent outer sheath of the fibres. 



Place a drop of osmic acid on one side of the slide and draw it under the coverslip by absorbing the salt solution 

 by blotting paper on the opposite side : then remove the blotting paper to prevent the osmic acid being 

 absorbed. Leave for fifteen minutes and examine. Observe the nodes of Ranvier in the fatly sheath and the 

 nuclei halfway between two nodes. 



u. Transverse Section of Sciatic Nerve prepared with osmic acid. Observe the grouping of the fibres 

 into bundles and the fatty sheaths as dark rings round the individual fibres. 



