80 C. J. HERRICK AND G. E. COGHILL 
It is evident that the arrangement above described provides 
for the entrance into the medulla oblongata of sensory impulses 
of very specific sorts which are segregated physiologically into 
distinct roots and each functional system has its own area of 
distribution into the secondary centers. But, on the other hand, 
the arrangment of the secondary neurones is such that they can 
transmit these ‘distinct physiological systems in separate form 
Fig. 10 Diagrammatic cross section through the medulla oblongata oflarval 
Amblystoma of the same age as figures 8 and 9, to illustrate types of connections 
of the secondary sensory neurones. The relations shown on the right side can 
be seen in a single section (cf. Herrick, ’14, figs. 38, 39, 40). The left side is a 
composite picture based on sections of different levels somewhat farther rostrad 
than the level shown on the right (cf. Herrick, ’14, figs. 34, 35, 36). For reference 
letters, see page 79. 
into the secondary correlation tracts only imperfectly, so that 
each of these correlation tracts may be actuated physiologically 
at the same time by two or more diverse physiological systems 
of the periphery—in the one case by both gustatory and tactual 
stimuli and in the other case by stimuli received from lateral 
line, vestibular (or auditory) and tactile organs. Before con- 
sidering the significance of these facts further, let us compare the 
corresponding mechanisms of the mammalian brain. 
