297 



classic treatise on tliis aiiiinal — empliasizes tlie absence of these 

 nerves. Whether the vagusroot is present lias to be settled still by 

 further research-work, in which also the periferal nervous system 

 in considered. 



Till now — only examining- the central nervous system and the 

 roots — it has been impossible to me to state the presence of this 

 root while Gustaf Retzius, thus confirming his father's opinion and 

 that of Johannes Muller, does accept a motor vagusroot, and — with 

 some reserve though — also a sensory root of the same. 



Renewed researches have made it probable to me that the roots 

 which these authors consider as vagusroots have to be regarded as 

 motor and sensory (occipito-) spinal nerx'es. 



This results from the fact that the cellular column from which 

 its rootfibres arise is the direct continuation of the column from 

 which the ventral roots of the spinal cord originate. Moreover the 

 more caudal spinal rootlets leave the cord in exactly the same 

 way as this so-called motor vagal root. ^) 



The absence of the entire glossopharyngeiis and first vagus root 

 in mentioned also for Bdellostoma Dombeyi by J. B. Johnston"). 



In. fig. 2 1 give a graphic reconstruction of the motor roots and 

 nuclei of Myxine glutinosa, made after the method used by Kappers'). 



If we compare this with the sagittal reconstruction of Petromyzon 

 fluviatilis ") (Fig. 1) we are struck by the peculiar character of 

 Myxine. 



The distance bstween the hind border of the entrance of the motor 

 fifth's root and the front border of the VIP^'s entrance is smaller 

 in Myxine than in Petromyzon, which proves that these roots have 

 approached each other in Myxine. The VII root is found already a 

 few sections behind the V''' . 



The closest approach has, however, occurred between the 



') That the dorsal root corresponding to this ventral root has to be regarded 

 as a vagus root is not very probable since it contains — as far as I can see — 

 only sensory fibres It is not a mixed root, as is always the case with the vagus. 

 For the same reason it is improbable tliat both the dorsal and the ventral root 

 should constitute together the vagus, on account of the fact that the vagus has 

 always a mixed character, its sensory and motor rootlets leaving the brain eitlier 

 together or on a very short distance, while tliese are opposed as real dorsal and 

 ventral roots. 



-) J. B. Johnston, Note on the presence or absence of the Glossopharyngeus 

 Nerve in Myxinoids. Anat. Record, Vol. 11, r.)08. 



■') Kappers, Verhandelingen der Kon. Akad. v. Wetenschappen te Amsterdam 

 1910, Tweede Serie, Deel 16, N". 4. 



^) From Kappers: Folia Neurobiologica Bnd. VI, Sommererganzungs Heft, 1912. 



