1909-10.] Nervous Mechanism of Alimentary Canal of the Bird. 339 
At this stage of development, therefore, sympathetic nerve cells and 
fibres were seen in front of the aorta, in the mesentery, and in the wall of 
the alimentary canal. The vagus fibres (line drawing) also entered the 
stomach wall at this age. 
The next stage of development examined was during the fifth day of 
incubation. At this age the sympathetic chain formed a more or less 
continuous line of cells behind the aorta. The migration of sympathetic 
Fig. 1. — L. S. chick at 4J days. A, vagus ; B, heart ; 
C, stomach with vagus fibres ; D, liver. 
nerve elements round the aorta was better marked (PL I. fig. 3), while 
in the pelvic region a network of sympathetic nerve cells and fibres 
indicated the position of a future plexus. From the lower or sacral 
portion of the spinal cord nerve fibres were seen growing out towards 
this rudimentary plexus. 
In the mesentery, numerous chains of nerve cells and fibres were found 
leading down to the gut wall (PI. I. fig. 4), while some of the larger 
abdominal aortic branches were accompanied by chains of those cells. In 
the stomach and intestinal wall the double layers of nerve elements were 
better marked, the nerve elements being more numerous and reacting 
better to the stain. The outer layer showed the nerve cells arranged in 
