184 MAMMALIA. 



branches of the sacral nerves, which are so intimately connected with the internal 

 pudendal, associates the various nerves of the lower portion of the intestines, the 

 kidneys and ovaries, and testes, and the several outlets and parts connected with the 

 completion of their functions. These nerves, as well as the rest of the sacral and 

 caudal, both anteriorly and posteriorly form the most extensive communications in the 

 body, and although the several parts furnished by them are connected together in 

 many functions, they can also be influenced by them separately. 



Although the mode of distribution of the sympathetic may be very similar, yet all 

 the ganglia and nerves may be modified by changes of structure for according with the 

 nervous system generally, or particular ganglia may have a more close or open texture 

 for assimilating with the required functions of any of the viscera : therefore by one 

 form throughout it may coincide with all the other nerves, or by a peculiar structure of 

 any of its ganglia be modified to changes in the viscera, and by the varied form of its 

 plexuses, connect together, in a greater or less degree, the organs in each region. Its 

 relation to the sanguiferous system and the great nervous centres deserves especial 

 notice. Its beginning is placed upon the internal carotid artery, branches ascend on 

 the vertebral from the inferior cervical and first thoracic ganglia, others accompany the 

 intercostal and lumbar arteries, and thus the bloodvessels of the brain, and every 

 portion of the spinal cord are brought under the same influence; it also regulates 

 the action of the bloodvessels generally, as well as those supplying the nerves them- 

 selves, to some distance at least, probably through the branches, which communicate 

 with all the spinal and some of the cerebral nerves, and thus keeps up a similar degree 

 of circulation between the nerves and their centres, and between them and the organs 

 of the body. 



The sympathetic nerve is supplied with blood by very small contiguous arteries, 

 and the vessels of the ganglia are only connected through other slender ones conducted 

 along the prolongation. The circulation in the ganglia is very moderate until they are 

 excited by the commencing activity of the organs on which these nerves are distributed, 

 or are made to partake of the plethora of their contiguous vessels. They chiefly retain 

 the colourless parts of the blood, but become very red from irritating causes, arising in 



