546 Dynamic Theory. 



and the hypoglossal nerves tenth and twelfth pairs cranial nerves. The fibres passing 

 from the great cardiac plexus, after being concerned in various complications of plex- 

 uses and ganglions, finally proceed to the heart and the great blood vessels, and follow 

 the latter throughout the system in all their subdivisions and ramifications. 



From the sixth, seventh, eighth and ninth, and sometimes the tenth, thoracic ganglia* 

 branches start out, descending inwards and uniting into a single trunk to form what is 

 called the great splanchnic nerve. It enters the abdomen, passes behind the stomach, 

 and divides into several branches which enter the semilunar ganglion. Thence numer- 

 ous filaments emerge to form the great solar plexus, which is situated on the vertebral 

 column,, the aorta, and the pillars of the diaphragm. The nerves issuing from this 

 plexus follow the aorta and all its branches, supply the liver, spleen, pancreas, kidneys, 

 testes and ovaries, and the muscular walls of the stomach and intestines. The lesser 

 splanchnic nerve, or renal nerve, is formed by two branches starting from the tenth and 

 eleventh thoracic ganglia, passing downward and inward, and uniting at the twelfth 

 dorsal vertebra into a single cord, which enters the abdomen through the diaphragm, 

 then divides into two branches, one furnishing fibres to the kidneys through the renal 

 plexus, and the other anastomosing with the great splanchnic nerve. The hypogastric 

 plexus is formed by fibres from the sacral ganglia, and by branches from the lumbar and 

 aortic plexuses. It sends off filaments which accompany the arteries that pass to the 

 bladder, urethra, vagina, rectum, &c. It is situated near the rectum. 



The sj'mpathetic S}'stem is called by plrysiologists, the < ' nervous sys- 

 tem of the automatic functions, " and the "nervous system of organic 

 life, " in distinction from the cranio-spinal system, which is called the 

 animal system. The vegetative, or automatic, functions are not under 

 the control of the will, and go on in spite of it. All the organs con- 

 cerned in these functions are reached by nerves from the sympathetic 

 nerve centers, and many of them have no other supply of nerves. This 

 is the case with the muscular coats of the small and large intestines, 

 and the gland ducts connecting with them, also the muscular walls of 

 the bladder, uterus, ureters, and fallopian tubes, also the greater part of 

 the glandular apparatus. (Carpenter.) But the heart and stomach, the 

 lachrymal, mammary, salivary and gastric glands are supplied by branches 

 from the cerebro spinal system, in- addition to those from the sympa- 

 thetic system, which are distributed on the walls of their blood vessels. 



The influence of the nerves of the animal system on the heart 

 and glands, has already been noticed. This influence is simply a 

 modifying influence, and has nothing to do with furnishing the motive 

 power by which these organs are operated. It has been repeatedly 

 pointed out that the power which causes the movements of the different 

 parts of the organized body, is derived from the chemistry of the diges- 

 tion of its food. The regulation of the movements, so that they may 

 support instead of antagonize and neutralize each other, depends upon 

 the influence of the motion of one part being communicated to that of 

 another part, that is, motion in one part must accelerate or retard the 

 motion of another with which it is in relation. This mutual influence 

 of the separated movements upon each other, is seen in animals that 

 have no nervous system, such as the hydra and actinia, and even the 

 amoebae. If a hydra be touched with a pin on one side, the effect is 

 communicated at once to all parts. But the touching with the pin is 



