120 NORMAL HISTOLOGY. 



b. Brain. In the way above described, cells should be 

 prepared from the gray cortical portion of the cerebrum 

 and cerebellum. 



c. Sympathetic. For the demonstration of these cells, 

 and the fibres connected with them, the frog answers 

 very well. The animal having been killed by breaking 

 up the medulla, the abdominal cavity is opened, and the 

 intestines and liver carefully removed ; the aorta will 

 then be seen lying along the vertebral column. The 

 sympathetic ganglia and nerves lie along the walls of the 

 aorta, and in the tissue surrounding the origin of the 

 spinal nerves. The head and forelegs should now be 

 cut off close behind the latter, and the hind legs severed 

 close to the body ; the trunk is then laid in a small dish, 

 and covered with equal parts of one-per-cent. solution of 

 osmic acid, alcohol, and water. The dish is covered and 

 set aside for twenty-four hours, when the aorta, together 

 with the tissue surrounding the commencement of the 

 spinal nerves, is dissected off in a single piece, spread on 

 a slide, and examined with a low power. Groups of sym- 

 pathetic nerve-cells are seen here and there in the speci- 

 men, and are readily distinguished by the orange color 

 of the cells : one or two of them are to be isolated 

 and freed as much as possible from the enclosing tissue, 

 carefully teased apart on a slide, stained lightly with 

 haematoxylin and then with eosin, and mounted in gly- 

 cerin. Successful preparations will show not only the 

 nerve-cells and non-medullated nerve-fibres, but also 

 the connection of the two within the capsule. 



