70 Transactions of the Academy of Science of St. Louis 
phylogenetic series, the motor neurons in the nervous system 
become correspondingly better developed. 
Malone (1912) pointed out that the neurons whose axons 
end in relation to the peripheral somatic motor neurons are very 
similar to the latter in structure. The structural features of 
somatic motor neurons are large size, polygonal form, and a 
chromidial pattern made up of rather large granules which are 
relatively regular in outline and uniformly distributed in the 
cytoplasm. He (1913) also asserted that the neurons whose 
axons supply skeletal muscle may be differentiated from visceral 
motor neurons by their cytological characters. Malone (1929) 
pointed out further that diffuse distribution of the chromidial 
substance is characteristic of afferent neurons, but efferent neu- 
rons with increased integrating capacity exhibit concentration 
of the chromidial substance into distinct granules and groups of 
granules. According to his findings the distribution of chro- 
midial granules in distinct, separate units is related to the capa- 
city of the neurons to integrate impulses from many diverse 
sources rather than to the volume of impulses received. He re 
ported that the preganglionic visceral neurons are cytologically 
similar to the premotor neurons. Of all the preganglionic 
visceral neurons, those of the dorsal vagus nucleus which supply 
cardiac muscle most closely approach the cytological structure 
of somatic motor neurons. These neurons have a smaller cell 
body, fewer and shorter dendrites, and a chromidial pattern in 
which aggregates of granules usually do not appear as distinct 
units. Like the motor neurons, they are polyhedral in form, 
but the less specialized visceral efferent neurons exhibit rounded 
forms. The latter also possess fewer dendrites and a chromidial 
pattern in which the granules are much less discreet. According 
to Malone, the cytological structure of these neurons is corre 
lated with the relative simplicity of visceral reactions. 
: Von Lenhossék (1887) was among the first to describe nuclei 
in the hypothalamus. He delimited the nucleus supraopticus 
and two nuclei in the tuber cinereum in man. One of the latter 
