SYMPATHETIC NERVOUS SYSTEM. 419 



ferior. n the chest, are the twelve thoracic ganglia, corre- 

 sponding to the twelve ribs. ' The great semilunar ganglia, 

 the largest of all, sometimes called the abdominal brain, are 

 in the abdomen, by the side of the coeliac axis. In the lum- 

 bar region, in front of the spinal column, are the four, and 

 sometimes five, lumbar ganglia. In front of the sacrum, are 

 the four or five sacral, or pelvic ganglia ; and in front of the 

 coccyx, is a small, single ganglion, the last of the -chain, 

 called the ganglion impar. Thus, the sympathetic cord, as 

 it is sometimes called, consists of from twenty-eight to thirty 

 ganglia on either side, terminating below in a single ganglion. 



Cranial Ganglia. The ophthalmic, lenticular, or ciliary 

 ganglion is situated deeply in the orbit, is of a reddish color, 

 and about the size of a pin's-head. It receives a motor 

 branch from the third pair, and sensory filaments from the 

 nasal branch of the ophthalmic division of the fifth. It is 

 also connected with the cavernous plexus and with Meckel's 

 ganglion. Its so-called motor and sensory roots from the 

 third and the fifth pair have already been described in con- 

 nection with these nerves. Its filaments of distribution are 

 the ten or twelve short ciliary nerves, which pass to the 

 ciliary muscle and the iris. A very delicate filament from 

 this ganglion passes to the eye with the central artery of the 

 retina, in the canal in the centre of the optic nerve. 



The functions of the ophthalmic ganglion are connected 

 exclusively with the action of the ciliary muscle and iris ; 

 and we will here do nothing more than indicate its anatomi- 

 cal relations, leaving its physiology to be taken up under the 

 head of vision. 



The spheno-palatine ganglion was first described by 

 Meckel, and is known as Meckel's ganglion. 1 This is the 

 largest of the cranial ganglia. It is of a triangular shape, 



1 MECKEL, De Ganglia secundi Rami quinti Paris Nervorum Cerebri nuper 

 detecto, Herolini, 1749 ; in LUDWIG, Scriptores Nevrofogici min&res selecti, Lipsiae, 

 1795, tomus iv., p. 7. 



