348 



PRACTICAL HISTOLOGY. 



[XXXI. 



(a.) Observe the shape of the cord, the decussation of the anterior 

 pyramids, i.e., bundles of fibres are seen coming from the lateral 

 column of one side, and running inwards and towards the middle 

 line, thus separating somewhat the anterior from the posterior 



corima (fig. 323). They actually 

 pass to the anterior pyramid of 

 the opposite side of the medulla. 



(b.) At the anterior part, on 

 each side of the anterior median 

 fissure, sections of the anterior 

 pyramid. 



((.) At the posterior part, a 

 small part of the posterior cornu 

 extending backwards as the 

 nucleus of the clava in the 

 FIG. 323.-T.S. Medulla Obiongata through funiculus gracilis. Another mass 



Decussation of Pyramids. D.Py. An- OI grey matter in the IliniCUlus 

 terior pyramid ; Fa. Anterior Cornu ; 

 Ng. Nucleus of the funiculus gracilis ; 

 g. Substantia gelatinosa ; XI. Spinal 





2. T.S. Of Oil Vary Bodies (L 



and H). Observe the folded mass 

 of grey matter, with many multipolar nerve-cells, constituting the 

 olivary nucleus (fig. 324); the complex of fibres, horizontal, vertical, 



and those cut longitudinally, 

 constituting the formatio 

 reticularis ; the much altered 

 arrangement of the grey 

 matter, which appears in the 

 floor of the fourth ventricle ; 

 and, according to the level 

 at which the section is made, 

 there may be met with the 

 origin of certain of the cranial 

 nerves (fig. 324). 



Of course sections should 

 be made from higher levels 

 in the medulla, and also 



through the pons. If a student has the requisite time, it is best to 

 make a series of sections from below upwards, fixing them in order 

 on slides. 



The two following tables show, the one the fissures, areas, and 

 mouldings to be noted on the medulla oblongata, and the other the 

 grey matter of the cord and medial a oblongata. 



.FIG. 324. T.S. Medulla Oblongata at the Level 

 of the Olivary Body ; partly Diagrammatic. 



