970 
not detected anything before close to the calamus. At this height, as 
has been mentioned above, we can see how the lateral pole of the 
nucleus motorius X dorsalis sends out eells in a ventro-lateral direc- 
tion (fig. 3). Laterally from nucleus XI these cells penetrate down- 
wards. The phenomenon is only to be observed in a few sections 
spinally and frontally from the calamus, after which the ambiguus, 
very poorly developed, appears. According my opinion we have here 
a proof that the nucleus ambiguus originates in the nucleus motorius 
dorsalis vagi, a theory which has been supported by Karpers on 
phylogenetic and ontogenetic grounds, and demonstrated by schemata 
in his work: “Weitere Mitteilungen iiber Neurobiotaxis. VII. Die 
phylogenetische Entwicklung der motorischen Wurzelkerne in Oblon- 
gata und Mittelhirn, Folia neurobiologica. Bnd. VI. 1912.” Through- 
out scores of sections the ambiguus is still poorly developed, and 
Fig. 6. Phocaena communis. 
only rarely it contains as many as 8, 10 or at the most 12 cells. 
Frequently we see a few cells perpendicularly under each other. 
Rather more frontally the development improves, and occasionally 
as many as 24 cells can be counted in two or three groups perpen- 
dicularly above each other. Then follow many sections in which we 
fairly constantly find 10—12 cells, after which a stronger develop- 
ment again commences at the place where the tongue nucleus is 
quite separate from the cervical grey matter. We then see two 
groups lying one above the other, the dorsal one containing not more 
than 8, and the ventral one at the most 15 cells; sometimes the 
dorsal group projects somewhat laterally. This order is repeated. In 
an entire series of sections practically nothing whatever is to be 
seen of the nucleus, after which a gradual development follows, 
when it begins to appear in several groups. 
Frequently we then see one dorsal, one ventro-lateral and one 
ventro-medial group, in other cases only one or two of these groups. 
At the frontal pole of nucleus XII the frontal outgrowth has already 
