NERVOUS CENTRES. (HUMAN ANATOMY. THE ENCEPHALON.) 



669 



corpora striota, he raised a large flap consisting 

 of the upper part of the hemispheres, with the 

 intervening corpus callosum and the adherent 

 fornix; and thus were exposed the inferior sur- 

 face of the latter, and the cavities of the three 

 ventricles, the fourth being shewn by a vertical 

 section of the cerebellum on the median plane, 

 and by the separation of the segments thus 

 made. This is an admirable section to display 

 the connection of the hemispheres with what 

 Willis described as the medulla oblongata, 

 namely, in the words of his translator, " all that 

 substance which reaches from the inmost cavity 

 of the callous body and conjuncture in the 

 basis of the head to the hole of the hinder part 

 of the head, where the same substance being 

 yet further continued ends in the spinal mar- 

 row." The fourth, seventh, and eighth plates 

 in Willis's work display this mode of dis- 

 section.* 



The modern researches of Reil, Gall and 

 Spurzheim, and others, directed attention more 

 particularly to the physiological anatomy of the 

 brain. Their principal object was to discover 

 the mode of connexion of the several segments 

 of the cord with each other, and of the whole 

 encephalon with the spinal cord. And their 

 method of dissection consisted in tracing the 

 course of the fibres chiefly from below upwards. 

 Reil found it necessary to harden the brain in 

 alcohol, in order to give it such firmness as 

 would enable him to tear portions of it in the 

 direction of its fibres, and thus to make these 

 latter conspicuous. There can be no doubt 

 that layers of the brain will separate most rea- 



* Thomae Willis, Cerebri anatome, nervorumque 

 descriptio et usus, in Opera Omnia, Amsterdam, 

 1682, cap. xiii. Also an English edition by S. 

 Pordage, London, 1684. The following extract 

 gives the description of Willis's dissection in his 

 own words. " (it cerebri ita proprie dicti anatome 

 rite celebretur, hand vulgari sectionis modo proce- 

 dendum esse existimo. Verum ubi totius fyxs<}>aXoi/ 

 calvaria exempli compages coram sistitur, im- 

 primis posterior cerebri limbus, ubi cerebello ac 

 medullas oblongat;e connectitur, membranis undique 

 discissis aut avulsis, a cohassione cum partibus sub- 

 jectis ^quantum fieri potest) liberetur ; tune facile 

 constabit quod cerebri substantia corporibus islis 

 haudquaquam unitur, verum per se, nisi quod 

 membranarum nexu superficie tenus conjungitur ab 

 iis omnino libera ac independens tuerit: quiuetiam 

 haec cerebii puppis a vicinis partibus eo ritu divisa, 

 si anterius reclinetur, medullas oblongatae crura, 

 prorsus nuda, ac a cerebro et cerebello (nisi in 

 quibus locis haec illi apoenduntur) omnino distincta 

 apparebunt. ***"'*********** 

 Interioris cerebri recessus adhuc clarius patebunt, 

 si limbus ejus a medullas oblongatae cohaesione, 

 quantum fieri potest, ex omni pane separatus et 

 elevatus, ad latera ejusdem medullae, quibus juxta 

 corpora striata unitur, puulo ulterius per substan- 

 tiam suam secetur, simulque fornix juxta radices 

 dtscissus una cum cerebro reflectatur, tune enim 

 cerebri compages penitus elevari, antrorsum re- 

 flecti, ac in planum explicari potest, ita ut corporis 

 callosi in aream latam expansi interior superficies 

 tola conspici et tractari possit. Ubi, praster medul- 

 larem et nitidissimam illius substantiam, observare 

 est plures lineas albas paralelas quas cerebri disse- 

 pimentum rectis angulis secant ; quasi essent trac- 

 tusquidam, sui vestigia, in quibus spiritus animales 

 ab uno cerebri haemispherio in alterum migrant 

 resiliuntque." Op. cit. cap. i. p. 5, 6. 



dily when torn in the direction of their fibres ; 

 and thus this mode of preparation becomes of 

 great importance to the anatomist, as he can 

 thereby determine easily the direction of those 

 fibres which form the principal portion of the 

 part under examination. It will not, however, 

 suffice to display the direction of all the fibres, 

 nor indeed is any mode of preparation adequate 

 for that purpose, which can only be accom- 

 plished by extensive and patient microscopic 

 investigation.* 



The great advantage of pursuing the dissec- 

 tion in the direction from below upwards con- 

 sists in this, that we proceed from the more 

 simple to the more complex. The problem 

 which the anatomist has to solve is, Given cer- 

 tain columns or bundles of fibres in the me- 

 dulla oblongata, to determine how they connect 

 themselves with the other segments of the brain. 

 But it is obvious that without some knowledge 

 of the topography of the other more compli- 

 cated parts of the encephalon, the dissector 

 would have considerable difficulty in pursuing 

 his researches. Nor must he content himself 

 with the solution of this fundamental question ; 

 he is to explore for other fibres in these seg- 

 ments besides those which connect them with 

 the medulla oblongata, and he has to ascertain 

 how they comport themselves, whether as form- 

 ing an integrant portion of the segment in which 

 they are found, or serving to connect it with 

 one or more of the others. 



Although we are mainly indebted to modern 

 anatomists for following out more completely 

 this method of dissection, it cannot be denied 

 that such men as Willis, Vieussens, and Mal- 

 pighi were quite alive to the importance of ex- 

 amining the fibres of the brain, with a view to 

 the physiological action of its different parts. No 

 one can J peruse Willis's admirable account of 

 the brain without perceiving how completely 

 he unites structure and function, and with what 



* Reil's methods of preparing the brain are best 

 described in his own words : " Of the methods 

 which I have employed in preparing brains, those 

 contained in the following directions answered best. 

 1. Let the brain be hardened in alcohol, and then 

 placed in a solution either of carbonated or pure 

 alkali, in the latter two days, in the former for a 

 longer period, and then again hardened in alcohol 

 it thus rendered too soft. The advantage of this 

 method is, that the fasciculi of nervous matter are 

 more readily separable, and the brown matter more 

 distinguishable from the white than after simple 

 maceration in alcohol; the grey matter is rendered 

 by the alkali of a blacker grey, and assumes the 

 consistence of jelly. 2. Let the brain be macerated 

 in alcohol, in which pure or carbonated potass or 

 ammonia has been previously dissolved ; the con- 

 traction of the brain is lessened by this process. 

 3. Let the brain be macerated in alcohol from six 

 to eight days, and then its superficial dissection 

 commenced, and the separation of the deeper parts 

 continued, as the fluid, in which the brain is kept 

 immersed, penetrates its substance. This method 

 appears tome belter than the preceding, and would 

 very likely be improved if the alcohol were ren- 

 dered alkaline. The fibres in a brain, thus pre- 

 pared, are more tenacious than otherwise, and the 

 deeper paris are sooner exposed to the influence of 

 the alcohol." Mayo's translation of Reil's Eighth 

 Essay, in the former's Anat. and Phys. Commen- 

 taries, p. ii. p. 50. 



