MAMMALIA. 185 



the system generally from diseases or poisons, or from the particular viscera they 

 supply. They become very much coloured when their vessels are disturbed after a 

 minute injection, but this appearance must not be considered as even in a moderate 

 degree approaching their ordinary condition in the healthy and quiescent state of the 

 organs they animate. 



In the human foetus, the sympathetic as well as the spinal nerves and their 

 ganglia are formed at an early period, and when very little more is apparent than the 

 membranes of the spinal cord. In a human foetus of about five months old, the 

 superior cervical ganglion was large, and the conjunction of the par vagum and ninth 

 had some similarity to a ganglion. The superior thoracic ganglion was large, but 

 could not be well separated from the inferior cervical ; all the other thoracic ganglia 

 were large and well defined, and had a distinct prolongation between them. The 

 origins of the splanchnic nerve were distinct ; the splanchnic nerve communicated with 

 the large renal capsule, and passed to the semilunar ganglion, which was very exten- 

 sive, and appeared to be formed more in globules than in the adult. The communica- 

 tion with the right phrenic nerve was seen, and all the plexuses were distinct on their 

 respective arteries ; the spermatic, however, was not satisfactorily traced. The poste- 

 rior trunk of the par vagum communicated with the coeliac plexus ; the hypogastric 

 proceeded to the bladder, and at this part seemed to give filaments about the passage 

 of the umbilical arteries. The spinal cord was nearly perfect, but reached to the 

 bottom of the sacrum, and all the spinal ganglia were large and well formed. In a 

 human foetus of about four months, the ganglia of the sympathetic throughout the 

 thorax were like patches of white cerebral matter, coalescing with each other, and, 

 from these, branches proceeded to the spinal nerves and the splanchnic. The other 

 ganglia were not satisfactorily observed. The spinal cord, however, was nearly 

 perfect, and its ganglia well formed, and there was a ganglion at the superior part of 

 the par vagum. The renal capsules were very large. In a human foetus of about 

 three months, the ganglia of the sympathetic were nearly the same as in that of four 

 months, as well as those of the spinal cord, but they were not so large. 



B B 



