376 



SPECIAL HISTOLOGY. 



the anterior half of the fourth ventricle, belongs properly to the pons 

 Varolii. It also contains, in its interior, besides the just described 



Fig. 147. 



elements, above the transverse fibre-layer, both in the middle as well as 

 more laterally, many accumulations of gray substance, with larger and 

 smaller (as much as 0*02 of a line and more) nerve-cells, all caudate, 

 which are so irregularly imbedded among the longitudinal and transverse 

 fibres, as to require no detailed description, and are connected on the 

 one side with gray nuclei of the medulla oblongata, and on the other 

 with the substantia nigra of the crura cerebri. 



The relations of the ten pairs of nerves which arise from the medulla 

 oblongata, the pons, and the crura, constitute a very difficult question. 

 But few inquirers have endeavored to solve it by other means than those 

 usually employed, that is to say, by the tracing of the fibres, with the 

 aid of the scalpel, which here goes no way at all. Among the excep- 

 tions are E, Weber (Art. " Muscular Motion," in Wagner's " Handw. d. 

 Phys." III. 2, pp. 20-22), who made his examination in preparations, 

 hardened by carbonate of potassa ; and Stilling, who pursued his by the 

 microscopical examination of sections, similarly hardened by means of 

 alcohol. My own results, obtained from preparations in chromic acid, 

 which had been for the most part made transparent by soda, agree in 

 almost every point with those of Stilling, which, at all events, among 

 all observations on the subject, have gone most deeply into the matter. 



Fig. 147. — Nerve-cells of the substantia ferrvgima in the floor of the fourth ventricle or 

 rhomboid fossa, of Man ; magnified 350 diameters. 



