780 DIRECTIONS FOB LABORATORY WORK 



(3) Sketch (110) a large nerve cell (e.g., large pyramidal cell of 

 cerebral cortex) in a demonstration slide prepared by the Beilschowsky 

 technic to show neurofibrils. 



(4) Sketch (111) a similar cell from a demonstration preparation 

 stained by NissFs method to show the chromophilic substance (Nissl 

 granules, chromophilic granules, tigroid substance). 



(5) Sketch also (112) from Golgi preparation (a) a large pyra- 

 midal cell of the cerebral cortex; and (113) (b) a Purkinje cell of the 

 cerebellar cortex. 



(B) THE AXON ("Nerve fiber"; Axis cylinder process; Neurite). 



(a) Medullated. (I) Tease in Ringer's solution a fragment of a 

 fresh medullated (myelinated) nerve (e.g., great sciatic; peroneal) from 

 a mammal or the frog. Mount under a cover-glass and study a well- 

 preserved fiber, noting the axial axis cylinder and neuroplasm, the en- 

 veloping medullary (myelin) sheath, the peripheral nucleated sheath of 

 Schwann (neurolemma), and the nodes of Eanvier. Add a drop of some 

 nuclear stain, and sketch (114). Are all of the fibers myelinated? Are 

 all of the same girth? 



(2) Tease a fragment of a medullated nerve preserved in osmic 

 acid. Mount and study an individual fiber, noting, besides the above- 

 specified constituents, also the Schmidt-Lantermann lines or incisures. 

 What is the significance of the Lantermann segments? Sketch (115). 



(3) Sketch (116) a small area from a stained cross section of the 

 white matter of the spinal cord. Note the central axis cylinder and the 

 enveloping myelin sheath, with its neurokeratin framework. Is a neuro- 

 lemma present? Note also the neurogliar connective tissue filling the 

 spaces between the fibers. 



(4) Study under l.p. a cross section of a large medullated nerve 

 (e.g., tibial; peroneal) in a stained preparation. Sketch (117) show- 

 ing epineurium, perineurium, funiculus, endoneurium, Henle's sheath, 

 and nerve fibers. Sketch h.p. (118) a small area of a funiculus. Are 

 all the fibers of the same girth? Sketch (119) also several fibers from 

 a stained transverse section of a medullated nerve preserved in osmic 

 acid. Chemical character of myelin? 



(5) Study under l.p. a longitudinal stained section of a medullated 

 nerve. Sketch (120) a small extent of two adjacent funiculi. Sketch 

 under h.p. (121) several adjacent fibers showing at least one node of 

 Ranvier. What are the criteria for distinguishing between longitudinal 



