THE MEDULLA OBLONGATA, OR AFTERBRAIN 



603 



Puncture with a sharp instrument of a certain spot in the medulla produces 

 diabetes (puncture diabetes of Cl. Bernard) in the animal suffering the opera- 

 tion. The mechanism concerned in this is quite unknown, but we may conclude 

 from the observed fact at any rate that in some way the medulla plays an essen- 

 tial part in the regulation of carbohydrate metabolism (cf. page 375). 



Although the medulla of the higher vertebrates cannot alone effect the coor- 

 dination of skeletal muscles necessary for locomotor movements, nevertheless 

 extensive motor effects, both reflex and automatic, appear more readily with the 

 medulla intact than when it is removed ; and we may imagine at least that this 

 influence of the medulla over the skeletal muscles is not without its significance 

 for their function as heat producers. 



Edinger observes that the centers which preside over the above-named and 

 other similar associations are probably to be sought among the multipolar 

 cells distributed through the substantia reticularis of the medulla, and de- 

 scribed by Bechterew as the nucleus reticularis tegmenti (Fig. 268). 



The medulla assumes a still higher dignity physiologically when we realize 

 that it contains the nuclei of origin of many efferent cranial nerves as well 

 as the nuclei around which the central endings of many afferent cranial nerves 

 split up. Named from below upward, these nerves are the hypo glossal, the 

 spinal accessory, the vagus, the auditory, the facial and the trigeminal (Fig. 

 269), although the last three and their nuclei do not belong exclusively to 

 the medulla. 



The efferent -fibers contained in these nerves supply the most widely dif- 

 ferent organs, but especially those which are most important for the vegetative 

 processes of the body; such, e. g., as the tongue, the salivary glands, the phar- 



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m. m.u. 



FIG. 269. Position of the nuclei of the cranial nerves, after Edinger. The medulla and pons are 

 supposed to be transparent. The cells of origin of the efferent nerves are black, the end- 

 nuclei of the afferent nerves red. 



ynx, oesophagus, stomach and intestine; the larynx, air passages and lungs; 

 the heart and blood vessels. The corresponding afferent fibers convey im- 

 pulses to the medulla from the internal car ; the skin of the face ; the mucous 

 membrane of the mouth inclusive of the tongue, the pharynx, oesophagus, 

 stomach and intestine ; the larynx, air passages and lungs ; the heart, etc. ; 



