2 26 NERVOUS SYSTEM. [sect. 113. 



are not continuously connected with each other — the unipolar cells, which 

 undoubtedly exist in many places for example — there is certainly no necessity 

 for assuming something of this kind in the case of the spinal cord, and by this 

 means render the isolated conduction of the nervous influence in definite 

 paths more inexplicable. 



The most recent Dorpat dissertations give very interesting information oil 

 the spinal cord of birds, of fishes, and of frogs ; still, as Stilling and I have 

 recently shown (see Z.f. Wiss. Zool., vol. ix.), they are in many respects 

 inexact. At all events, we must be on our guard in applying these relations 

 to the human cord without farther investigation. Tn the lower vertebrata, 

 the gray substance evidently contains connective tissue, and from this cir- 

 cumstance On'sjannikow supposes that it also occurs in man. This is, in 

 fact, the case, inasmuch as I find throughout the whole gray substance, cells, 

 which present the character of plasm-cells, and lie in a more homogeneous 

 stroma. In the white substance besides, areolar tissue undoubtedly accom- 

 panies the vessels. 



§ 113. The Medulla Oblongata and Pons Varolii belong to the 

 most complicated parts of the central nervous system, and contain 

 white and grey substance, intermingled in very various ways. 

 Besides the well-known bundles of white substance, as the •pyra- 

 mids, olivary bundles, etc., whose, description is given in every 

 hand-book of Anatomy, it contains a peculiar system of horizontal 

 fibres, which appear to me, in part, to pass from the restiform 

 bodies and the peduncles of the cerebellum into the anterior part 

 of the medulla oblongata (see Stilling's work and my Micros. 

 Anatomy). All bundles of the white substance consist of parallel 

 nerve-tubes of the same dimensions as those of the cord. 



The gray substance is found collected in the medulla oblongata, 

 especially at three places : 1. In the olivary bodies it forms the 

 well-known folded lamina constituting a capsule, which is shut on 

 all sides except the inner, and consists of smaller stellated nerve- 

 cells, and fibres of the horizontal system traversing them. 2. In 

 the restiform bodies the gray substance is not sharply defined, and 

 occupies especially the fasciculus lateralis. It is a continuation of 

 the posterior horns of the spinal cord, and even presents an indi- 

 cation of the substantia gelatinosa. 3. The gray substance at the 

 bottom of the fourth ventricle, is a continuation of the anterior 

 parts of the gray substance of the cord, and forms a tolerably thick 

 layer extending from the calamus scriptorius to the aquaiductus 

 Sylvii. It' contains numerous nerve-tubes in part of very con- 

 siderable size, up to o'Oo6'", or even o"Oo8'", in part of the 

 finer ami finest kinds; besides these, nothing but multipolar 

 nerve-cells from o*oo6'" up to o - 03'" and more. The ala cinerea 

 and substantia ferruginea possess the largest cells, and in the 



