1909-10.] Nervous Mechanism of Alimentary Canal of the Bird. 327 
XVII. — The Development of the Autonomic Nervous Mechanism of 
the Alimentary Canal of the Bird. By Williamina Abel, M.D., 
Carnegie Scholar. (From the Physiological Department, University 
of Glasgow.) (With Four Plates.) 
(MS. received December 17, 1909. Bead January 24, 1910.) 
Introduction. 
Concerning the development of the ganglia and plexuses in the intestine, 
various theories have from time to time been formulated. The older 
writers, among whom were Remak (1, 2), Gotte (5), Balfour and Foster 
(6), assumed that they had a mesoblastic origin, were formed in situ, and 
became joined on to the main sympathetic chain at a later date. 
Later, an ectodermic origin was generally recognised as belonging to the 
central nervous system, but writers were not agreed as to the origin of the 
sympathetic. A few, among whom were His (4), Birdsall and Schenk (8), 
maintained that its origin was, like the central nervous system, ectodermic, 
but many held the older view that it was a mesoblastic structure. Among 
those who held the latter view, some regarded the sympathetic chain as the 
basis of the visceral ganglia, while others held that the visceral ganglia 
were developed in situ, and joined later to the main sympathetic 
chain. 
At the present time the work of His junior (12, 13, 14) on the embryonic 
chick affords valuable evidence that the sympathetic chain is an outgrowth 
from the intervertebral ganglia, and that the different ganglia in the 
intestine are derivatives of it. This work of His has borne out many 
points given in the earlier writings of His senior (11) and Onodi (9). 
Viewing the question from the standpoint of histology, the balance is 
at present in favour of the outgrowth theory — or, in other words, of the 
theory that the visceral ganglia and plexuses of the intestine are out- 
growths of the sympathetic chain, which is in turn derived from the inter- 
vertebral ganglia. But the evidence is by no means conclusive. 
When the question is, however, considered from the standpoint of the 
physiological work of Bayliss and Starling (19) on the intestine, and of 
Elliot (21) on the innervation of the urethra and bladder, the peculiar 
independence of the peripheral ganglia from those of the central nervous 
system seems so marked as to justify Elliot in suggesting the possibility 
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