1909-10.] Nervous Mechanism of Alimentary Canal of the Bird. 331 
as superseding a primary sympathetic chain in the lower cervical and 
thoracic regions was recognised. In the abdominal region the sympathetic 
network in front of the aorta was well developed, while in the wall of the 
intestine the two layers of nerve plexuses were easily recognised. 
At the tenth day the abdominal sympathetic was found well developed. 
In this paper also a short account was given of the development of the 
abdominal sympathetic in the human embryo. 
In 1899 Dogiel (15) published the results of an examination made by 
him on the minute anatomy of the plexuses in the intestinal wall. In this 
article he also gave an interesting resume of the most important publica- 
tions dealing with this subject. The staining methods with methylene 
blue used in his own examination are described in detail. As a result of 
his observations, Dogiel classified the nerve cells in the ganglia of the 
intestinal wall into three varieties. The first or motor type was found 
most abundantly in the Auerbach plexus, the second or sensory type lay 
mostly in Meissner’s plexus, while the third type was not restricted to either 
plexus, and seemed to possess characteristics of both the first and second 
types. The nerve fibres in the ganglia were also classified into two groups, 
detailed descriptions of which are found in this article. 
In 1904 Graham Kerr (16) described the early development of motor 
nerves in Lepidosiren. The development of a motor nerve was traced back 
to a protoplasmic bridge extending between the medullary tube and the 
myotome. That is, the motor nerve exists from the first as a protoplasmic 
band between the spinal cord and the end organ. At first this band is 
naked, but later it is covered with mesenchymatous protoplasm laden with 
yolk. As development proceeds the yolk is used up, and the protoplasm 
with its nuclei extends into the substance of the nerve trunk. This forms 
the protoplasmic sheath of the nerve. 
Harrison (17), in an account of transplantation experiments made in 
connection with the problem of nerve development, described the following 
results : — 
1. Limb ends of tadpoles transplanted to various parts of normal 
individuals develop normally, and are supplied by nerves from the 
host which supply the region in which the transplantation was 
effected. 
2. Limb ends taken from “ nerveless ” tadpoles, when transplanted into 
a normal individual, are supplied in an exactly similar manner. 
Reference was also made to a series of experiments made by Harrison 
and Lewis, in which they showed that transplantation of a ganglion to a 
nerveless region resulted in the development of radiating nerve fibres ; and, 
