HTMAN AND MAMMALIAN. 35 



form a true olivary commissure, they are constantly accompanied by the arciform 

 fibres, which here, as elsewhere, decussate in so great number, connecting the vari- 

 ous parts of the medulla with those of the opposite side. 



Schroder van der Kolk^ and Lenhossek^ have described at considerable length a 

 large and well marked bundle, called by the latter '■^ pedunculua olivce" serving to 

 connect the olivary body with the hypoglossal nucleus, with the roots of which it 

 is nearly parallel. " These fibres arise from the gray substance of the olivary body, 

 and form a tolerably large bundle, which does not differ much in thickness from 

 the roots of the hj^oglossal, and which we can follow uninterruptedly into the 

 nucleus of this nerve. The fasciculi in question appear not to perforate the olivary 

 body, as they do not appear on the other side; but they arise, as can be easily 

 shown, from the ganglionic cells of the olivary body itself. They pass through 

 the hilus, and are collected in bundles, which run into the hypoglossal nucleus."^ I 

 have nowhere been able to find such bundles as are figured by Schroder van der 

 Kolk (op. cit., Fig. 14, Plate v), or by Lenhossek (op. cit., Fig. I, Plate ii), with 

 their fibres spreading out like a brush into the hilus, my own observations on this 

 point being very closely in agreement with those of KoUiker.* As stated by hin^ 

 the roots of the hypoglossal do not always run in front of the olivary bodies, but 

 frequently penetrate the lamina at a greater or less depth, and often pursue a wavy 

 or zigzag course before emerging (Figs. 26, 27, 21", 22"). It of course often hap- 

 pens that such bundles are cut off, and may easily be mistaken for fibres originating 

 in the hilus, and when we take into consideration the slightly ascending course of 

 the hypoglossal roots, which may be easily demonstrated in longitudinal sections, 

 the probability becomes very great that the bundles seen in the upper part of the 

 medulla apparently terminating in the hilus (Figs. 22", 24") are mainly cut off bmi- 

 dles of hypoglossal roots which emerge lower down.* 



The fibres from the hUus and from the cells of the lamina pass in every direction, 

 both forwards towards the raphe, and transversely towards the posterior portion of 

 the medulla, contributing to form the very beautifid and complicated network with 

 which the entire anterior and antero-lateral portions of the medulla, between t\ie 

 nuclei on the floor of the fourth ventricle and the olivary bodies, is filled. The cells 

 found in this network are mostly single, though sometimes collected into little 

 groups which serve to unite the distant parts of the medulla, and seem especially 

 intended to connect the olivary bodies with the hypoglossal nucleus, perhaps also 

 with that of the spinal accessory, though I have never been able to trace any direct 

 communication between this and the olivary column, notwithstanding the assertion 

 of Schroder van der Kolk. 



At points where the hypoglossal roots cross the olivary lamina, it becomes very 

 difficult to decide whether or not any connection is brought about between the 



^ Medulla Oblongata, 164. ^ Neue TJiitersuelmngen, 34. 



= Schroder v. d. Kolk, 1. c. 134. » Gewebelehre, 1862, 321. 



5 This opinion is further confirmed by the figures given by Stilling and Clarke, in which no such 

 bundles as are represented by Lenhossek are to be found. (See Stilling, Medulla Oblongata, pis. v and 

 vi, and Clarke, Philos. Trans. 1858, figs. 29, 30, 31, 32, and especially fig. 36.) 



