CHAPTER XI 



THE GENERAL SOMATIC SYSTEMS OF CONDUCTION 



PATHS 



IN this and the following chapters we shall review the con- 

 duction pathways followed by some of the chief sensori-motor 

 systems and add some further details to the general description 

 already given, beginning with the more generalized somatic 

 sensory functions. 



Clinical neurologists have long been in the habit of grouping 

 together the different forms of deep and cutaneous sensibility 

 under the term "general sensibility." The more refined re- 

 searches of recent students (especially Sherrington, Head, 

 Trotter and Davies, Brouwer, see the bibliographies on pp. 

 94 and 142) have given us a much more precise analysis 

 of these systems, as already explained. The peripheral 

 nerves of deep sensibility (exclusive of those devoted to 

 strictly visceral functions) are anatomically distinct from 

 those of cutaneous sensibility. Physiologically, the nerves of 

 deep sensibility are devoted chiefly to proprioceptive functions 

 (muscle sensibility, joint sensibility, etc.), and the nerves of 

 cutaneous sensibility chiefly to exteroceptive functions (touch, 

 temperature, and pain); but this holds only approximately, for 

 nerves of deep sensibility may also serve the exteroceptive func- 

 tions of pressure and painful response to overstimulation, 

 though with a higher stimulus threshold than in the skin, and the 

 cutaneous nerves also participate to some extent in the proprio- 

 ceptive functions of spatial orientation of the body and its mem- 

 bers (see pp. 77 ff. and 132). 



Exteroceptive Systems. The nerves serving the functions 

 of touch, pressure, temperature, and pain of the body and 

 limbs, whether derived from the skin or the deep tissues, im- 

 mediately after their entrance into the spinal cord terminate in 



172 



