LYMPH SPACES. 191 



until the mode of preparing sections and of injecting 

 the bloodvessels had been explained. 



Injected muscular tissue is obtained from any 

 injected limb, and should be hardened in strong 

 alcohol. If the piece is not large enough to hold 

 in the fingers, it must be embedded, and moderately 

 thin sections made both longitudinally and trans- 

 versely, and mounted, unstained, in dammar. 



Transverse sections of a nerve-trunk may be 

 made from any large nerve that has been hardened 

 in picric acid (forty-eight hours), and subsequently 

 in alcohol. The sections are to be stained with 

 picro-carmine (twenty-four hours), and may be 

 mounted in glycerine. By this method the medul- 

 lary sheath of the nerves and the elastic tissue of 

 the perineurium and epineurium are stained yellow, 

 the connective tissue lamellae and bundles pale red, 

 and the corpuscles and nuclei and the axis cylinders 

 a darker red. 



Longitudinal sections of a nerve-trunk from an 

 injected limb may be prepared in the same way as 

 those of injected muscle. 



The lymph spaces which lie between the lamel- 

 lae of the perineurium of the nerve, and extend also 

 amongst the fibres within the funiculi, can very 

 readily be injected with 2 per cent, solution of 

 Berlin blue by merely sticking a very fine injecting 

 canula into a funiculus, and employing moderate 

 pressure. The injection runs along the course of 

 the nerve almost as freely as if it were an open tube. 

 A piece of nerve which has been injected in this 

 way is to be cut out, hardened in spirit, and trans- 

 verse sections prepared and mounted in dammar, 

 without staining, to show the course taken by the 

 injection. At the entrance of the nerve-roots into 

 the spinal canal the perineural clefts communicate 

 with the sub-arachnoid space, so that the nerves can 

 be injected by merely forcing the injecting fluid into 

 this. 



