650 OLFACTORY NERVES AND ORGANS OF VERTEBRATES. 
decree prohibiting the importation into Portugal of pork 
from the United States in every shape in consequence of 
trichinosis/ 5 
In consequence of the report of their Medical Officer of 
Health, the Dunmow Rural Sanitary Authority have issued 
a placard warning the public and cautioning sellers of pork. 
Extracts from British and Foreign Journals. 
DEVELOPMENT OF THE OLFACTORY NERVE AND 
OLFACTORY ORGAN OF VERTEBRATES. 
The Edinburgh Medical Journal says that in the course of 
an investigation by Dr. Milnes Marshall into the development 
of the cranial nerves of the chick, certain facts came to light 
indicating that the olfactory nerve, instead of being, as usually 
described, a structure differing totally in its mode of origin 
from all the other nerves in the body, in reality “ exactly 
corresponds in mode of development with the other cranial 
nerves, and with the posterior roots of the spinal nerves/ 5 * 
The presentpaper contains the results of further investigations 
on this point; it deals also with some features in the develop¬ 
ment of the vertebrate olfactory organ, and with certain 
questions of a more general nature affected by the conclusions 
arrived at. 
The Development of the Olfactory Nerve. —The olfactory nerve 
of an adult vertebrate is usually described as consisting of 
three parts; a proximal tractus olfactorius , an intermediate 
bulbtis olfactorius , and a distal nervus olfactorius , connecting the 
bulb with the olfactoryForgan. Of these parts the two former 
are commonlv said to arise as a hollow diverticulum of the 
cerebral hemisphere—the so-called olfactory vesicle or olfactory 
lobe. The third part, the nervus olfactorius , is described as 
arising at a later stage, either from the olfactory lobe, from 
the olfactory organ, or from the intervening mesoblast. In 
consequence of these peculiarities in its mode of development, 
the olfactory nerve is said not to bear the slightest resemblance 
to the other cranial nerves, and to be in no way comparable 
with them. Dr. Marshall,how r ever, finds from an examination 
of a large number of vertebrate embryos—chick, dog-fish, 
* Proc. Roy. Soc., 8th March, 1877, p. 50, and Quarterly Journ. of 
Micros. Science, January, 1878, pp. 17—23. 
