372 CEREBRO-SPINAL NERVES. 
this, is the pnewmogastric nerve, or par vagum (10), which 
supplies the lungs and air-passages, and also the heart and 
stomach. Below this, again, is the hypoglossal nerve (11), 
which gives motion to the tongue ; at 12 is a nerve termed 
the spinal accessory, which is concerned in the acts of respira-_ 
tion; and at 13 and 14 are two of the regular spinal nerves. 
The termination of all these nerves is either in that prolonga- 
tion of the Spinal Cord into the cavity of the skull, which is - 
termed the Medulla Oblongata (fig. 197, 7’), or in the Sensory 
Ganglia which are closely connected with the upper part of 
this prolongation. Although some of them seem to pass 
directly into the Cerebrum, it is very doubtful if such is really . 
the case. 
460. A general connected view of the Brain and Spinal 
Cord is given in fig. 197 ; which represents the front of the — 
latter, with the Brain a ‘turned back, so as to expose its — 
under side. At 4 is seen its anterior lobe; atc its middle 
lobe ; and its posterior lobe d@ is almost entirely concealed by 
the Cerebellum e. At f’ is shown the Medulla Oblongata, 
or upper end of the Spinal Cord ff The brachial plexus 
is seen at g, formed by the nerves that originate in the cervical 
region of the cord; at A is the lumbar plexus formed by the 
nerves of the lumbar portion; and at & is the sacral plexus” 
formed by the sacral nerves. The spinal cord terminates at 
its lower extremity in a bundle of nerves j, to which the name ~ 
cauda equina is given, from its resemblance to a horse’s tai 
The various pairs of nerves from 1 to 14 are the same as in 
the preceding description; 15 and 16 are nerves from the 
upper part of the cervical region ; 25, a pair from the dorsa 
region ; and 33, a pair from the lumbar region. All these | 
spinal nerves find their way out through apertures in the 
vertebral column, which are formed by a union of two notches, 
one in each of the adjoining vertebre. | 
461. The system of nerves which has been now deserib of 
is termed the Cerebro-Spinal; but it is not the only set of 
nerves and ganglia contained within the bodies of Vertebrated 
animals. In front of the vertebral column there is a chain of 
oblong ganglia, which communicate with two large ganglia 
that lie among the intestines, and with several small ganglia 
in the head and other parts. They communicate also with 
posterior roots of the spinal nerves, on which are another 
