Cytological Structure, Hypothalamic Nuclei, Functional Connections 77 
HyPoTtHaLaMic NUCLEI CONTAINING CENTRAL SOMATIC 
EFFERENT NEURONS 
Nucleus Hypothalamicus Lateralis: The neurons of this 
nucleus are somewhat scattered but form a fairly definite ag- 
gtegate which extends throughout most of the lateral portion 
of the tuber cinereum and lies lateral and dorsolateral to the 
fibers of the medial forebrain bundle (Fig. 3 A). The central 
Somatic efferent neurons are not segregated but lie among the 
central visceral efferent and associational neurons which form a 
Part of the nucleus. According to Malone (1912), the neurons 
in this nucleus which are similar cytologically to somatic motor 
neurons are continuous caudally with the superior colliculus and 
the reticular substance of the brain stem. 
Nucleus Mammillaris Lateralis: This nucleus is located 
along the ventral margin of the mammillary body just lateral to 
the medial mammillary nucleus (Fig. 3 D). Nearly all of its 
constituent neurons are of the central somatic efferent type. 
They tend to be a little less polyhedral and more spherical than 
those of the nucleus hypothalamicus lateralis. Both with respect 
to morphology and chromidial pattern they are very similar to the 
motor cells of the anterior horn in the spinal cord. Some 
central visceral efferent and’ associational neurons are present. 
Nucleus Hypothalamicus Dorsalis: This is a diffuse mass 
of neurons found in the dorsal part of the posterior portion of 
the tuber cinereum (Fig. 3 B). It is bounded medially by the 
third ventricle and laterally, in part, by the mammillo-thalamic 
'ract. The central somatic efferent neurons which are present are 
very similar to typical anterior horn cells, but they are sages d 
few in number. The great majority of the neurons are of the 
associational and central visceral efferent types. Those of 
the latter type contribute fibers to the periventricular system 
(Gurdjian, 1927). 
