216 



PRACTICAL HISTOLOGY. 



[XVIIT. 



eyeball there issue a few fine threads, branches of the fifth nerve. 



Scoop out the brain. These threads are readily recognised by being 



usually somewhat pigmented. With a pair of scissors make a snip 

 in the base of the skull at right angles to the cut 

 already made. Turn up the bone, and on the fifth 

 nerve, which runs towards the foramen behind 

 the eyeball, will be found a small oval swelling 

 surrounded by a tough capsule. Divide the latter 

 and remove the ganglion. I have usually found 

 that the little ganglionic swelling is somewhat 

 pigmented. At any rate, it is easily found by 

 tracing the fifth nerve backwards. The nerve is 

 accompanied by an artery. 



Tease the ganglion in .25 per cent, osmic acid, 

 and let it stain in this fluid for two hours. Stain 

 it for several hours in picro-carmine (under a 

 moist - chamber, p. 82), tease a fragment in 

 glycerine. Try to find a cell with its single pro- 

 cess prolonged into a nerve-fibre. In most of the 

 cells, however, the process is apt to be detached. 



7. Sympathetic Ganglia (Frog). Lying in 

 contact with the spinal column of the frog is a 



FIG. 200. Nerve-Ceil row o f sma ]i semi-transparent ganglia, the sym- 



from Rabbit's 



Spinal Ganglion, pathetic chain, and between them and the roots 

 ceii^ca^uie^n 6 ^ ^he spinal nerves pass fine nerve filaments. 

 Nucleus of nerve- Open the abdomen of a freshly-killed frog, re- 



flbre ; a. Nerve- ,-, . , ,. , , , i i* . j_-i i 



fibre; Fibre di- move the intestinal tract and liver, cut through 

 the peritoneum above the kidneys, raise the 

 kidneys and excise them. There will be seen 

 the white nerves issuing from the cord. Between 

 these and the sympathetic ganglia fine nerves run transversely. 

 Cut out the sympathetic ganglia and treat them with chloride of 

 gold by the method (p. 79, 3) ; or cut out the aorta and the 

 adjacent tissues, and subject them to the gold chloride method. 

 After the piece of tissue has acquired a purplish colour, examine 

 it with a low power to find nerve-cells. The nerve-cells may be 

 isolated or arranged in groups. It requires great care to get a satis- 

 factory preparation. Note the pyriform shape of the cell, each with 

 a large nucleus, the cell-substance continued into a straight process, 

 which may be seen to be encircled by a spiral process. The body 

 of the cell is surrounded by a well-marked capsule, which is con- 

 tinued over the cell-processes, and has nuclei on its inner surface. 



8. Sympathetic Ganglion (Mammal) (H). Harden the first 

 thoracic sympathetic ganglion or the superior cervical ganglion of a 

 man or rabbit in 2 per cent, ammonium bichromate (2-3 weeks), 



viding at e at. a 

 node of Ranvier, 

 T-shaped fibre. 



