1890 - 97 .] 
Chairman's Opening Address. 
185 
gland; or (3) with the dendrons of another neuron in the im- 
mediate vicinity of the first, or at a great distance from it. It is 
to he noted, however, that the arborization of two axis-cylinders 
never come into close relationship with each other. Further, no 
direct continuity can he established between neurons. The den- 
dritic processes may closely approach the terminal arborizations of 
an axis-cylinder; and, in turn, the terminal arborizations of an 
axis-cylinder may closely approach the dendritic processes of 
another neuron, or the body of a nerve cell, or the cells of a 
secreting gland, or, as in the end plates in muscle, the contractile 
tissue, hut there is never anatomical continuity. If we could 
detach a neuron, and pick it out from its bed nothing would he 
ruptured. Another remarkable fact brought out by the new method 
is that both axis-cylinders and dendritic fibrils often give off at 
right angles extremely fine fibrils, and that these fibrils end in 
delicate dendritic-looking processes by which they are brought into 
relation with other neurons. 
Further, the researches of Golgi, Cajal, Kolliker, and many 
others, appear to show that all the central nervous organs are built 
up of neurons, each constructed on the same type, and that the 
varying degree of complexity of the structure of any part of the 
cerebral nervous organs depends on the complexity in detail of the 
neurons composing it. Thus, spinal cord, cerebellum, cerebrum, 
and the nervous portion of the special terminal organs of sense, 
such as the retina, the organ of Corti with the ganglion of the 
lamina spiralis , are all constructed on the same genera] plan. 
They are aggregations of neurons, arranged with reference to each 
other in a special way. It also appears that one portion of a neuron 
may be a considerable distance from another. Thus a neuron in 
one of the grey layers of the cerebrum may be related, by its 
dendritic processes, to the upper layers of the cortex, and, by its 
axis-cylinder process, and the terminal arborizations of the latter, 
to the dendritic processes of a motor neuron in the anterior horn of 
grey matter in the lumbar region of the spinal cord. It appears 
to me that a great step has been taken in this recognition of a 
morphological nervous unit. 
"We now turn to the physiological side of the question. Writers 
are, on the whole, of opinion that nervous impulses are conveyed 
