84 INTRODUCTION 



7. The Spinal Cord. Procure at a slaughterhouse a spinal cord of 

 an ox and examine it fresh, or preserve it in one of the fluids men- 

 tioned in the preceding section. Preserved portions can be used later 

 in a more careful study of the structure of the cord. 



8. The Sympathetic Nervous System. If the abdominal cavity of a 

 dog, cat, rat, or frog be opened and the viscera displaced, there may be 

 seen on each side of the backbone a white cord with grayish enlarge- 

 ments, ganglia. The two cords and their ganglia constitute the main 

 chains of the sympathetic system. 



9. Nerve Fibers. Tease out with needles in water on a glass slide 

 a small piece of a nerve. Even without the aid of a lens the nerve is 

 seen to be composed of small, threadlike fibers. Examined with the 

 compound microscope the fibrous structure will become more apparent. 



