THE SPINAL MARROW AND ITS FUNCTIONS, 143 



a. The convolutions of the cerebrum. 



b. The laminae of the cerebellum. 

 e. The pons varolii. 



g. The medulla oblongata. 



c. d. f. The medulla spinalis, or spinal marrow, extending from the 

 first cervical to the first lumbar vertebra, and terminating in the cauda 

 equina. The cerebrum, it will be seen, is the largest portion of the 

 brain, and occupies the whole upper cavity of the skull. It rests an- 

 teriorily upon the arches of the orbits ; in the centre, upon the middle 

 fossae of the base of the skull, and posteriorily upon the tentorium 

 cercbclli. 



Questions. How do we find the brain developed in the lower ani- 

 mals ? Have they great tenacity of life /"? Will zoophytes live when 

 divided into pieces 1 What is the medulla oblongata ? What its func. 

 tion ? Describe the spinal cord ? its membranes ? its shape ? its 

 structure ? How many pair of nerves arise from it ? How many from 

 the neckf the back/t the loins ; What is the function of the ante- 

 rior roots ? the posterior roots ? What is the use of the spinal cord ? 

 How is this illustrated ? How proved ? What follows, if the spinal 

 cord be severed opposite the second bone of the neck ? the fifth ? the 

 first dorsal ? Does the principle of motion reside to any extent in the 

 spinal cord itself ? What experiment proves this ? Why does a divi. 

 sion of the par vagum or eighth pair cause death ? Does the spinal mar- 

 row exert any influence on the circulation of the blood ? on the capil- 

 lary circulation t<rt-on digestion ? What proves this ? Has it any in. 

 fluence over the kidneys ?-s-over nutrition ? 



