LEPUS 



157 



autonomic (sympathetic and parasympathetic) nerves from the 

 remainder, is the fact that in the autonomic system the muscles 

 and glands are not connected directly with the brain or spinal 

 cord by a single nerve-cell, but by two, one reaching from the 

 brain or cord to the sympathetic (or parasympathetic) ganglion, 

 and the other continuing from this ganglion to the muscle or 

 gland in question. Such muscles are always smooth and 



de.~- 



SCL.— i 



c: 



EC 



Fig. 67. — Diagram showing the structure of the ear in mammals. 



ac, auditory capsule ; c, cochlea ; de, ductus endolymphaticus ; Et, 

 Eustachian tube ; jo, fenestra ovalis ; fr, fenestra, rotunda ; i, incus (quad- 

 rate) ; m, malleus (articular) ; oe, external auditory meatus (outer ear) ; 

 s, stapes (columella auris, hyomandibula) ; sa, saccule ; sc, semicircular 

 canal ; tc, tympanic cavity (middle ear) ; tm, tympanic membrane (ear- 

 drum) ; «, utricle. 



involuntary. Striped (voluntary) muscles are innervated 

 direct from the brain or cord by nerve-cells which go all the 

 way without interruption. 



As in lower forms, the ganglia of the sympathetic trunk are 

 connected with the spinal ganglia by rami communicantes. 



The diaphragm contains muscles of somatic origin which 

 are innervated by the phrenic nerves. These nerves are 



