334 



ANATOMY IN A NUTSHELL. 



columnar ciliated epithelium in the fetus, but in the adult the cilia have dis- 

 appeared and fill the canal with their remains. It is continuous above with the 

 fourth ventricle of the brain. This canal is the remains of the original neural 

 canal of the embryo, from the walls of which the spinal cord is formed. The 

 sinus rhomboidalis inferior or ventricularis terminalis is a dilatation of the cen- 

 tral canal in the conus medullaris. 



Diseases of the spinal cord may affect its entire transverse area, or certain 

 portions of it in varying lengths, or it may begin at any level and extend up- 

 ward or downward, in which case, being designated as ascending or descending. 



PLATE CL1V. 



RIGHT LOBE' 



BILE DUCT 



The Inferior Surface of the Liver. 



A tumor would be an example of a focal disease, or disease of one of the seg- 

 ments (a portion of the cord with a pair of nerves). Locomotor ataxia is an 

 example of a systemic disease. 



Fractures of the spinal column above the fifth cervical vertebra — above the 

 origirj of the phrenic nerve, are almost always fatal because of paralysis of the 

 diaphragm. Fractures of the fifth, sixth, and seventh vertebrae cause paraly- 

 sis of the intercostal and abdominal muscles and death usually results. 

 In fractures of the Lower part of the thoracic region the prognosis is not 

 so unfavorable. Degenerations in motor tracts of the cord descend, and 

 the sensory tracts ascend. This is due to the fact that the trophic centers of 

 the m«>ti»r tracts are in the okay matter of the brain, while those of the sen- 

 sory iraci- arc in the G \m.li \ upon the posterior roots of the spinal nerves. 

 In the crossed pyramidal tracts we find three sets of fibers, motor, vasomotor, 





