HERRICK, (Verve Components. 303 
our most fundamental division in the analysis of the nervous 
system ; viz.: (1) the somatic systems (sensory and motor) for 
bodily responses to external stimuli, and (2) the visceral systems 
(sensory and motor) for visceral reactions to internal stimuli. 
Each of these great divisions has been analyzed periph. 
erally, more or less imperfectly as yet, into systems of compo- 
nents, as suggested above. Every such system of nerve fibers 
performs a separate function, conducts a single type of nervous 
impulse, either afferent, i. e., sensory, or efferent, i. e., excito- 
motor, excito-glandular, etc. The following systems are already 
distinguishable anatomically : 
I. Somatic SYSTEMS. 
1. Tactile, or general cutaneous, 
2. Acustico-lateral, including nerves for lateral line organs (in the Ich- 
thyopsida) and for organs of equilibration and hearing (in verte- 
brates generally). These organs and their nerves have probably 
been derived phylogenetically from the general cutaneous system 
and, like the organs of the latter type, are adapted for the recep- 
tion of various kinds of mechanical impact, either rhythmic or 
non-rhythmic. 
3. Visual (a system of uncertain relationships, provisionally classified 
under the somatic sensory). 
4. Somatic motor, for the innervation of skeletal or voluntary muscles. 
II. VIscERAL SYSTEMS. 
5:  Vusceral sensory, unspecialized sensory nerves of the viscera, distrib- 
uted chiefly through the sympathetic nerves. 
6. Gustatory, innervating specialized sense organs (taste buds) of chem- 
ical sense probably derived phylogenetically from the preceding 
type. 
7. Olfactory (provisionally classified here because of the apparent resem- 
blance between taste and smell). 
8. Visceral motor, distributed chiefly to unstriped and involuntary mus- 
cles, generally through the sympathetic system. 
9. ELxcito-glandular, provisionally classified here because of genera — 
resemblance to the last mentioned type. 
There are numerous other systems which can be differen- 
tiated physiologically, but which cannot as yet be completely 
separated anatomically and classified, such as nerves for the 
