38 GRAY SUBSTANCE OP THE MEDULLA OBLONGATA 



the cells of the olivary bodies, and in many cases are doubtless continuous with 

 their processes, so that the probability deduced by Clarke, from the study of trans- 

 verse sections, viz., that " the olivary bodies axe co-ordinating centres for the different 

 ganglia or nuclei of the medulla oblongata" derives additional strength from the 

 study of the laminse in the beautiful convolutions in which we find them arranged 

 in their longitudinal course. 



The olivary bodies are connected most intimately with the great system of longitu- 

 dinal fibres running on each side of the raphe, by means of which parts lying above 

 and beloio are brought into co-ordination. The tico sides of the medidla are also 

 united by the intimate relation existing between the olivary bodies and the arciforra 

 fibres, as well as by means of the olivary commissure ; while posteriorly the olivaries 

 receive radiating fibres from the nudei lying along the floor of the fourth ventricle^ to 

 which they are still further united by means of the internal and external bundles 

 of arciform fibres, Avhich bend around them and also enter them, forming such an 

 intricate plexus in the antero-lateral portions of the meduUa (Plate XV). Their 

 relations with the anterolateral nuclei are very close and intimate, as also with the 

 caput cornu,, and in the anterior portion of the medulla, fibres are everywhere seen 

 turning off, especially in longitudinal sections, towards the outer layer of marginal 

 fibres. 



Whether or not it is true, as Todd and Bowman have surmised, " that the olivary 

 bodies constitute the essential portion or nucleus of the medulla oblongata, that on 

 which its power as an independent centre depends,"^ it is evident that they are very 

 largely concerned in the co-ordination of actioff, bringing into harmony the most 

 distant parts of the medulla, and appearing to stand, in connection with the system 

 of arciform fibres, much in the same relation to the nuclei of the medulla oblongata, 

 as the cerebellum and fibres of the pons Varolii do to the nuclei of that part of the 

 central nervous system to which they belong. 



' Physiological Anatomy, I, 26T. 



