THE MAMMALIAN NERVOUS SYSTEM 63 



constantly refer to the intact human brain for the relations of 

 the nerve-roots and other external landmarks. 



(During the examination of these sections it will be helpful 

 for the instructor to demonstrate with the projection lantern all 

 of the sections to be studied and point out some of the more im- 

 portant structures. Individual tracts should be followed 

 through the series of sections, passing the entire series in review 

 many times for this purpose.) 



4. Internal Structure of the Spinal Cord 



63. General histology of the neuron. (a) Procure from the 

 slaughter-house a portion of the spinal cord of a freshly killed 

 beef (the cord of any other one of the larger mammals will 

 answer) . Each student should dissect out a small portion of 

 the substance of the ventral gray column (ventral horn) and 

 tease it out with needles on a clean glass slide until it is spread 

 in a thin layer. Cover the fresh tissue with a few drops of a 

 solution of methylene-blue (1 part to 10,000 parts of water) 

 and stain for fifteen minutes. Rinse off the stain, add a drop of 

 water, and cover with a cover-slip. Examine with low and 

 high powers of the microscope and draw a typical neuron with 

 its processes. 



(b) Now lay out all of the slides of stained and permanently 

 mounted sections of the spinal cord supplied in the loan collec- 

 tion of microscopic material and examine them to get a general 

 view of its internal structure. Compare sections through the 

 spinal cord prepared by different histological methods (Wei- 

 gert, Nissl, Golgi, Cajal, etc.) and note which histological ele- 

 ments are best revealed by each of the methods used. Draw 

 on a large scale typical neurons from the ventral gray column 

 from several of these preparations. Look up the technic em- 

 ployed in these methods and the purposes for which each is 

 best adapted. On the study of pathological degenerations and 

 the embryological development of fiber tracts see Section 68 

 (b) and (c). A thorough neurological study of any part re- 

 quires the use of several histological methods, since each of 

 them is specific for some elements only of the tissue. 



(c) Literature on the neuron: Barker ('10), Chapters I to 



