THE CENTRAL MARROW. 211 



of this organ. As it alone can give us the most important 

 information as to the nature of our " mind," it commands 

 our most earnest attention. For if the central marrow 

 develops in the human embryo exactly as in the embryos 

 of all other Mammals, then the development of the human 

 mental organ from the same central organ of other Mammals 

 and, more remotely, from that of lower Vertebrates, cannot 

 be questioned. It is, therefore, impossible to dispute the 

 enormous significance of these phenomena of development. 



In order to appreciate these rightly, a few words must 

 first be said as to the general form and anatomical construc- 

 tion of the developed central marrow in Man. Like the 

 central nervous system of all other Skulled Animals (Cra- 

 niota), it consists of two distinct parts : firstly, of the brain 

 or the medulla of the head (encephalon, or medulla, ca- 

 pitis), and, secondly, of the spinal marrow (medulla spi- 

 nalis). The former is enclosed in the bony skull, or " brain 

 case," the latter in the bony vertebral canal, which is com- 

 posed of a consecutive series of vertebrae, shaped like signet 

 rings. (Of. Plate V. Fig. 16, ra.) From the brain proceed 

 twelve pairs of head nerves, from the spinal marrow thirty- 

 one pairs of medullary or spinal nerves for the remainder 

 of the body. The spinal marrow, when examined merely 

 anatomically, appears as a cylindrical cord with a spindle- 

 shaped swelling in the region of the neck (at the last of the 

 neck-vertebrae) and another in the lumbar region (at the 

 first lumbar vertebra, Figs. 217, 218). At the swelling at 

 the throat the large nerves of the upper limbs pass off from 

 the spinal marrow, and those of the lower limbs from the 

 swelling in the lumbar region. The upper end of the spinal 

 marrow passes through the neck-marrow (medulla oUon- 



