336 Dr. Foville's Researches on the Atiatoviy of' the Brahi. 



simply resulting fj-om anatomical structure, acquire a vast ad- 

 ditional importance when they are taken in conjunction with 

 innumerable facts, which prove that the derangements to be 

 observed in the brains of those who have laboured under men- 

 tal alienation (without complication), are constantly to be found 

 on the surface of the organ, that is in the cineritious matter of 

 the convolutions. At the same time it is generally known 

 that those diseases of the brain which more })articularly affect 

 motion, have their seat in the median or internal parts. These 

 observations obviously support the analogy which I have 

 pointed out as existing between the brain and the spinal cord. 



I must not allow myself to enter into longer details on this 

 point, but proceed to consider the influence which the know- 

 ledge of this anatomical structure of the brain may have on 

 the pathology of this organ. 



Pathological Part. 



It is evident that the better we are acquainted with the struc- 

 ture of an organ in its healthy state, the more capable shall 

 we be of appreciating the alterations which it may undergo. 

 In other words, healthy anatomy is the true basis of morbid 

 anatomy. The observations which I have collected show the 

 importance of this general truth, in relation to the brain in 

 particular. 



The separation of all the planes of which I have spoken is 

 easily effected in healthy biains. In young children they may 

 be said to be simply in juxta-position. We may remark in 

 the interval between them a thin layer of very fine, extremely 

 soft, and highly vascular cellular structure, which is probably 

 a continuation of the vascular membrane at the exterior of the 

 brain. 



In the healthy brains of adults these planes are more inti- 

 mately united together; but their separation may alvyays be 

 easily and neady effected if we proceed with care. This is by 

 no means the case in many diseases of the brain. I have often 

 in vain attempted to separate the planes. They were as inti- 

 mately adherent as the pleura pulmonalis to the pleura cos- 

 talis after inflammation of the surfaces ; and the attempt to se- 

 parate them had invariably the effect of tearing them. 



How was this alteration to be recognized when the struc- 

 ture on which its existence depends was unknown ; and how 

 often, from this very cause, have diseased brains been examined 

 without the slightest trace of derangement having been dis- 

 covered ? 



But I must suspend these very summary considerations, 

 which I have brought forward rather to set forth the advantages 



which 



