84 



SPINAL MARROW. 



which extends below through the whole spine, but 

 above does not proceed farther than the point where 

 the rachidian bulb joins the tuber annulare ; and that 

 this column gives origin to a particular order of 

 nerves the respiratory; The corpora olivaria, and 

 the posterior corpora pyramidalia, are regarded by 

 Mr. Solly 1 as ganglia; the former of the function of 

 respiration, the latter of the sense of hearing. 



The anterior and upper half of the medulla ob- 

 longata bears the names pons Varolii, tuber annu- 

 lare, and nodus cerebri; and to this are attached, 

 superiorly, the corpora or tubercula quadrigemina. 

 In the very centre of the pons, the crura cerebri 

 bury themselves ; and by many, they are considered 

 to decussate ; by others, to be prolongations of the 

 anterior column of the spinal marrow. Sir C. Bell 

 thinks, that the pons Varolii stands in the same re- 

 lation to the lateral portions of the cerebellum, that 

 the corpus callosum does to the cerebrum ; that it 

 is the great commissure of the cerebellum, uniting 

 its lateral parts, and associating the two organs. 



The medulla oblongata consists chiefly of the cen- 

 tres of the nerves of respiration and deglutition, 

 which, as elsewhere shown, are strictly reflex in 

 their action. 



2. The spinal marrow extends, in the vertebral 

 canal from the foramen magnum of the occipital 

 bone above to the first or second lumbar vertebra, 

 where it terminates in the cauda equina. It is 

 chiefly composed of medullary matter, but not entire- 

 }y so- Within, the cineritious substance is ranged 

 . immediately below irregularly, but has a crucial form when a section 

 py e ramids Ssa B ti0 At middle is made. The marginal illustrations exhibit sections 

 of cervical buib. c. Mid- O f the spinal cord of man at different points; and 



way between cervical . . i i -^ 



and lumbar bulbs. D. the proportion oi gray and white matter at each. 



lblb ' E 'vy From the calamus scriptorius in the fourth ventricle, 



pos- an( * tne r i ma formed by the corpora pyramidalia be- 



surface. The fore, two fissures extend downwards, which divide 



points of emergence of, ., -,1,1 L' mi j. 



the anterior and poste- the spinal marrow into lateral portions. Ihe two 

 ntJSSfcSf. the nerves lateral portions are divided into an anterior and a 

 posterior, so that the cord has four distinct portions. 

 By some, indeed, it is conceived to consist of three columns an anterior, 

 posterior, and a middle or lateral. 



The vertebral canal is lined by a strong ligamentous sheath, running 

 down its whole length. The dura mater likewise envelopes the medulla 

 at the occipital foramen, being firmly united to the ligaments ; but far- 

 ther down it constitutes a separate tube. The tunica arachnoidea from 



1 The Human Brain, its Configuration, Structure, Development, and Physiology, &c., p. 

 147, London, 1836. See, on this subject, Dr. John Reid, on the Anatomy of the Medulla 

 Oblongata, in Edinb. Med. and Surg. Journ., Jan., 1841, p. 12. 



