HUMAN AND MAMMALIAN. 33 



which they appear to be closely connected. In longitudinal sections, the lower 

 portion of the olivary column presents a similar appearance, consisting of successive 

 layers of scattered ceUs, separated from each other by thick bundles of transverse 

 fibres, penetrating the column in every direction. Higher up, the cells are more 

 and more compactly arranged, soon becoming collected into a convoluted lamina, 

 the form of which has so often been drawn and described. 



The principal changes in the general form of the olivary bodies are well shown 

 in Plates VII and XV. In Plate VII, Fig. 25, a section is seen soon after the fuU 

 development of the convolution is attained, at a point just above the opening of the 

 fourth ventricle, some additional details being given in Plate XV, Fig. 20"/ The 

 olivary body, which in the preceding figure, 19", consisted of a closed convolution 

 in the centre of a large fibrous mass, is now an open series of folds, with very 

 numerous transverse fibres radiating towards the centre or hilus, across which 

 the hypoglossal roots pass ; the fibrous mass within and around the lamina still 

 hoAvever predominating. In Fig. 26, Plate VII, the convolutions have become 

 much deeper and closer, the course of the fibres proceeding frcSn the interior is 

 much more distinct, and many of them may now be seen passing directly forwards, 

 towards the raphe, where they decussate with their feUows from the opposite side, 

 forming a commissure between the two olivary bodies. In this course they are 

 joined by numerous arciform fibres, which everywhere surround and penetrate the 

 olivaries, forming an exceedingly complicated plexus radiating from the posterior 

 portion of the medulla. 



From this stage upwards, the principal changes consist in the rapid increase 

 in number and size of the convolutions, which soon occupy nearly the entire 

 mass of the olivary column (Plates VII and XV, Figs. 27, 28, 22", 23", 24"). In 

 the outline figures (Plate XV) I have merely attempted to indicate the relation of 

 the arciform fibres to the lamina, these fibres forming so intricate a plexus as they 

 pass through the convolutions of the lamina, either joining cells or passing onwards 

 towards the decussation at the raphe, that anything more than the merest indication 

 of their course would have required the use of many additional figiures on a much 

 larger scale than those given. 



In the neighborhood of the olivary bodies will be noticed several smaller nuclei, 

 occasionally assuming the convoluted form to some extent. These bodies, called by 

 Stilling^ the accessory olivary nucleus (Oliven-Nebenkern) and larger pyramidal 

 nucleus (grosser Pyramiden-Kern), have been shown by Clarke^ and Schroder van 

 der Kolk* to be similar in structure to the olivaries, and are undoubtedly groups 

 of similar cells, more or less removed from the main body, but identical in structure 

 and relations. Moreover, as Schroder van der Kolk has pointed out, the so called 



* Figs. 20, 20" and 26 are from the same section ; Fig. 26 is from a section a very little higher 

 than Figs. 21, 21" ; Fig. 21 is also from a section a little higher up than Figs. 22, 22", but they may 

 be regarded as representing substantially the same level ; Figs. 23, 23", and 28 are from the same 

 section. 



» Medulla Oblongata, 30, 31. = Philos. Transactions, 1858, 243. 



* Medulla Oblongata, 133. 



5 



