MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 
235 
sympathetic plexus. Of these two great ganglia, the larger (f), that of the right side, 
receives likewise a distinct branch from nerve (^) of the visceral siipra-oesophageal 
ganglion, and thus these gastro-hepatie centres are brought into relation with the 
cerebro-spinal centres. These two cardiac centres are the chief links of a complete 
chain or collar of ganglia* and commissures that surround the posterior or cardiac 
end of the stomach, just behind the oesophagus, and at the entrance of the great 
duct of the liver. There are ten or twelve, or more centres in this collar, and from 
it, branches are given off on both sides, and chiefly from the centres ; these pass 
forwards on the stomach, and backwards on the hepatic duct to the liver ; the latter 
are fine, and form with small ganglia an intricate plexus on the duct ; these have 
not been followed into the liver on account of the extreme delicacy of the parts ; the 
former are larger, and four of them, which may be regarded as principal trunks, pass 
forwards upon the different aspects of the stomach, forming, with microscopic fila- 
ments and ganglia, a complete interlacement all over that organ, particularly on its 
under surface. The pancreas also is crowded with almost microscopic ganglia and 
filaments. We propose to denominate the whole of this very extensive and compli- 
cated network, of which the circular collar of ganglia may be considered as the 
centre, the gastro-hepatie plexus of the sympathetic system. Altogether it forms, 
with its almost countless orange-tinted ganglionic nodules of various forms and sizes, 
a novel anatomical spectacle of extraordinary beauty and interest. These nerves 
and ganglia are visible without much difficulty in a favourable specimen, and lie for 
the most part slightly imbedded on the external surface of the organs. Towards the 
pyloric end of the stomach the ganglia are thickly strewn, presenting the appearance 
of another collar or circle around that part : this may be called the pyloric plexus 
(«)'!'. From this there is a continuous minute and singularly beautiful plexus of 
nerves and ganglia, dowm the whole length of the intestinal canal to the anus. These 
ganglionic nodules are usually smaller on the whole than the gastric, varying less in 
size and in form, being mostly globular, and having the same orange colour. They 
are most numerous at the two extremities of the intestine ; taken as a whole, they 
may very properly be called intestinal plexus (w, w)\. 
The branchial or branchio-cardiac portion, as far as we have observed, consists of 
a somewhat irregular chain of large orange ganglia and nerves lying across, and in 
front of the base of, the branchial crown, and over the hepatic vein. Twigs pass 
backwards from this to the branchial plumes, and forwards towards the heart, and two 
branches of communication (gand j) are received from the visceral supra-oesophageal 
ganglion. A twig reaching these ganglia laterally from the mantle nerve of each 
side keeps up a connection between them and the branchial supra-cesophageal 
centres. 
An open network {v) with two ganglia has been observed on the floor of the renal 
organ, and over the hepatic vein ; this is all we have found to represent a renal plexus, 
* Plate XVIII. fig. 1. -|- Plate XVIII. fig. 2. 
^ Plate XVIII. fig. 4. 
