16 OHIO STATE ACADEMY OF SCIENCH. 
I. Somatic SYSTEMS. 
1. Tactile, or general Cutaneous. 
2. Acustico-lateral, including nerves for lateral line organs (in the 
Ichthyopsida)’and for organs of equilibration and hearing (in 
vertebrates 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 reception of various kinds of mechanical 
impact, either rhythmic or non-rhythmic. 
3. Visual (a system of uncertain relationship, provisionally classi- 
fied under the somatic sensory). 
4. Somatic motor, for the innervation of skeletal or voluntary 
muscles. 
II. VisceraL SYSTEMS. 
5. Visceral sensory, unspecialized sensory nerves of the viscera, dis- 
tributed chiefly through the sympathetic nerves. 
6. Gustatory, innervating specialized sense organs (taste buds) of 
chemical sense, probably derived piysee meta from the 
preceding type. 
7. Olfactory (provisionally classified here because of the apparent 
resemblance betwen taste and smell). 
8. Visceral motor, distributed chiefly to unstriped and involuntary 
muscles, generally through the sympathetic system. 
9, Excito-glandular, provisionally classified here because of general 
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 
thermal sensations, muscle sensations, etc., but enough has been 
done to enable us to lay down the general plan or pattern of the 
peripheral nervous system as a whole and to define the main path- 
ways by which stimuli of different modalities reach the brain and 
are reflected back to the responsive organs. Our anatomical knowl- 
edge of these pathways is sufficiently well controlled by precise 
physiological experimentation to enable us to state with confidence 
that each of the nine systems mentioned above is a real functional 
unit. 
The fibers composing these systems may reach the central 
nervous system through a series of many nerve roots arranged 
in a segmental way, like the general cutaneous nerves of the 
spinal cord, or they may all be represented in a single large 
nerve, like the optic and olfactory. Thus it happens that some 
nerves, like those last mentioned, are “pure” nerves, while others, 
like the facialis or vagus, are “mixed,” containing in some cases 
as many as four anatomically distinguishable components. 
