Cytological Structure, Hypothalamic Nuclet, Functional Connections 83 
chromidia are relatively coarse and, in the majority of the cells, 
are aggregated in the perinuclear or the peripheral zone. 
morphology and chromidial pattern of these neurons suggest local 
functional connections. 
Nuclei Hypothalamicus Periventricularis Dorsalis and Ven- 
tralis; ‘These nuclei are closely associated. The nucleus hy- 
pothalamicus periventricularis ventralis is located at the most 
ventral margin of the hypothalamus, immediately lateral to the 
third ventricle and dorsolateral to the cavity of the infundibular 
stalk. The nucleus hypothalamicus periventricularis dorsalis 
ccupies a position just dorsal to the latter nucleus and is incom- 
pletely separated from it (Fig. 3 B). Both are made up of 
typical associational neurons. The chromidia commonly have a 
Peripheral distribution, but in some cells they are aggregated in 
the perinuclear zone. According to Gurdjian (1927), these nuclei 
Probably contribute fibers to the periventricular system, at least 
in their posterior portions. 
Nucleus Interstitialis: This nucleus lies dorsal to the fibers 
of the supramammillary decussation and among them (Fig. 3 D ). 
Although the neurons are predominately associational, a consid- 
erable number of central visceral efferent neurons are present. 
Data regarding the functional connections of this nucleus are 
Wanting. 
SUMMARY and CONCLUSIONS 
The results of the present study support the assumption 
that the neurons in the hypothalamic nuclei can be classified in 
four categories according to their functional relationships. These 
have been designated peripheral visceral efferent, central somatic 
efferent, central visceral efferent, and associational. 
Peripheral visceral efferent neurons are Se by 
medium or large size, spherical or polyhedral shape, coarse chro- 
