200 HEAD AND NECK 



The white matter of the medulla spinalis increases steadily 

 in quantity from below upwards. 



The fasciculi gracilis and cuneatus, which form the posterior funiculus 

 of the medulla spinalis, are composed of fibres which enter the spinal medulla 

 as the fila of the posterior nerve-roots. In the lower portion of the medulla 

 spinalis the two fasciculi are not marked off from each other. 



In the lateral and anterior funiculi of the adult spinal medulla it is not 

 possible with the naked eye to distinguish the different strands of fibres of 

 which they consist, but the student should remember that such strands or 

 tracts are present. The three best-defined tracts in the antero-lateral part 

 of the spinal medulla are, (i)the fasciculus cerebello-spinalis (O.T. direct 

 cerebellar tract) ; (2) the fasciculus cerebro-spinalis lateralis (O.T. crossed 

 pyramidal tract) ; (3) the fasciculus cerebro-spinalis anterior (O.T. direct 

 pyramidal tract). 



The fascictilus cerebello-spinalis ascends to the cerebellum, but, traced 

 in the opposite direction, it is found to disappear in the lower thoracic region 

 of the medulla spinalis. The fasciculus cerebro-spinalis lateralis occupies 

 a larger district of the medulla spinalis. It is placed in the lateral funiculus 

 anterior to the posterior column of grey matter and immediately medial to the 

 fasciculus cerebello-spinalis. -As the fasciculuscerebello-spinalis disappears in 

 the lower part of the medulla spinalis the fasciculus cerebro-spinalis lateralis 

 comes to the surface, and it can be traced as low as the fourth sacral nerve. 

 T\& fasciculus cerebro-spinalis anterior forms the narrow strip of the anterior 

 funiculus, which lies immediately adjacent to the antero-median fissure. It 

 reaches down to about the middle of the thoracic region of the medulla 

 spinalis and then disappears. 



After the body has been five days on its face it will be 

 replaced upon its back with the thorax and pelvis supported 

 by blocks, and the dissectors of the head and neck should at 

 once proceed to clean the temporal fascia, and afterwards to 

 remove the brain and study the interior of the cranium. 



Dissection. Take away the anterior and superior auricular muscles and 

 remove the thin layer of fascia subjacent to them which descends from 

 the lower border of the galea aponeurotica to the zygomatic arch. When 

 this has been done the strong temporal fascia will be exposed. Note that 

 it is attached above to the temporal ridge and below to the upper border 

 of the zygomatic arch. The details of its connections will be studied at 

 a later period. 



REMOVAL OF THE BRAIN. 



After the superficial attachments of the temporal fascia 

 have been noted the dissectors of the head and neck should 

 proceed to remove the brain. 



Dissection. The head being supported upon a block, extend the median 

 incision, already made in the galea aponeurotica, to the nasion anteriorly and 



