THE SKIN AS AN ORGAN OF SENSATION 87 



114. In the neck, loins, and pelvis adjacent nerves 

 interlace with one another to form a plexus, or network. 

 In a plexus nerve fibers from two or more nerves are 

 brought into connection in such a way that the parts of 

 the body which receive nervous fibers from the plexus 

 have communication with a greater number of nerve trunks 

 and nerve centers, and may receive more complex im- 

 pulses, than do those parts to which branches go from 

 but a single nerve trunk. This is why these plexuses 

 are so frequently found in connection with the nerves 

 going to the limbs, where great complexity of motion and 

 careful coordination are required. 



The nerves of the skin form plexuses in the dermis. 

 In some parts of the body these contain fibers from spinal 

 nerves and also from certain of the cranial nerves. From 

 these plexuses minute nerve fibers pass to the papillse, 

 which contain the tactile end organs. 



115. Tactile End Organs. End organs are those pecul- 

 iarly formed nerve cells or groups of cells which receive 

 and pass on the stimulus to which 



they are adapted. Tactile end organs 

 are of several different forms. 



Pacinian corpuscles are found deep 

 in the dermis, scattered along the fine 

 nerve branches like buds on a plant. 

 Each corpuscle consists of layers of 

 delicate membrane within which is a 

 single minute nerve fiber (Fig. 50). 

 Another form of end organ, called the 

 touch corpuscle, appears especially in Fl S- 50. Pacmian 

 the papillae of fingers and toes, and is 

 much smaller than the Pacinian corpuscle. The touch 

 corpuscles are oblong masses, each containing a capsule 



