NERVOUS CENTRES. (Human Anatomy. Tut Encepuaton.) 
corpora striata, 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 
Yentricles, the fourth being shewn by a vertical 
ection of the cerebellum on the median plane, 
by the separation of the segments thus 
ade. 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 
bf the callous body and conjuncture in the 
isis 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- 
Tow.” The fourth, seventh, and eighth plates 
in Willis's work display this mode of dis- 
the modern researches of Reil, Gall and 
sim, and others, directed attention more 
rticularly to the physiological anatomy of the 
fain. Their principal object was to discover 
e 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 
urse of the fibres chiefly from below upwards. 
Reil found it necessary to harden the brain in 
cohol, in order to give it such firmness as 
ould enable him to tear portions of it in the 
ection of its fibres, and thus to make these 
er conspicuous. There can be no doubt 
yers of the brain will separate most rea- 
* Thomz Willis, Cerebri anatome, nervorumque 
‘descriptio et usus, in Opera Omnia, Amsterdam, 
$2, 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. ‘* Ut cerebri ita proprie dicti anatome 
rite celebretur, haud vulgari sectionis modo proce- 
ndum esse existimo. Verum ubi totius eyxepadov 
aalyaria exempti compages coram sistitur, im- 
imis posterior cerebri limbus, ubi cerebello ac 
medallz oblongatw connectitur, membranis undique 
iscissis aut avulsis, a cohesione cum partibus sub- 
tis (quantum fieri potest) liberetur ; tunc facile 
abit quod cerebri substantia corporibus istis 
quam unitur, verum per se, nisi quod 
branarum nexu superficie tenus conjungitur ab 
ino libera ac independens fuerit: quinetiam 
f ri puppis a vicinis partibus eo ritu divisa, 
Si anterius reclinetur, medulle oblongate crura, 
Prorsus nuda, ac a cerebro et cerebello (nisi in 
appurebunt. illi appenduntur) omnino distincta 
; bunt, * * * * * FX 
eee Ee 
s cerebri recessus adhuc clarius patebunt, 
ms ejus a medullw oblongate cohesione, 
mtum fieri potest, ex omni parte separatus et 
vatus, ad latera ejusdem medulle, quibus juxta 
ra striata unitur, paulo ulterius per substan- 
lam secetnr, simulque fornix juxta radices 
ssus una cum cerebro reflectatur, tunc enim 
" compages penitus elevari, antrorsum re- 
lecti, ac in planum explicari potest, ita ut corporis 
callosi in aream latam expansi interior superficies 
en ganeb et tractari possit. Ubi, preter medul- 
et nitidissimam illius substantiam, observare 
est plures lineas albas paralelas que cerebri disse- 
| pimentum rectis angulis secant ; quasi essent trac- 
_ | tus quidam, sui vestigia, in quibus spiritus animales 
ab uno cerebri hamispherio in alterum migrant 
Tesiliuntque.” Op. cit. cap. i. p. 5, 6, 
| si 
669 
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 topesraphy 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 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 solntion either of carbonated or pure 
alkali, in the latter two days, in the former for a 
longer period, and then again hardened in alcohol 
if 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 to me better 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 parts 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, 
