HYPER J3MIA OF THE BRAIN AND ITS MEMBRANES. 179 



and still more so whether those of the cerebral substance, have been 

 more than normally filled with blood during life. Mistakes in the 

 account of the autopsy are frequent. 



The mistakes regarding the amount of blood in the cerebral mem- 

 branes depend partly on the fact that, when unaccustomed observers 

 find the vessels much distended at the dependent parts of the surface 

 of the brain, they diagnose a hyperaemia of the cerebral membranes, 

 even if the blood has only sunk downward, and the vessels in the upper 

 part be empty. Still more frequently another error is committed even 

 by practised observers : that is, from a similar distention of the vessels 

 on the convex surface of the cerebrum, hyperaemia of the cerebral 

 membranes is decided on without looking further. It should be borne 

 in mind that the arteries supplying the cerebral membranes with blood 

 lie at the base of the brain, and that only very fine arterial twigs reach 

 the convexity of the greater hemispheres. All the large blood-vessels 

 usually seen on the surface of the brain, when the skull is opened, are 

 veins. Distention of these veins is a normal appearance, if the indi- 

 vidual has died of an acute disease by which his blood was not con- 

 sumed, or, if he has. died suddenly from suffocation, acute poisoning, 

 or from some other accident involving no loss of blood. Hence it is 

 entirely wrong, in such cases, to decide, from the overfilling of the 

 veins, that there has been hyperaSmia of the brain or its membranes 

 during life, and to connect this pretended hyperaemia with the symp- 

 toms that have been observed. In the history of the post mortem^ 

 accounts of excessive hyperaemia of the brain and its membranes are 

 often combined with others of a similar excessive hyperaemia of the 

 lungs, liver, kidneys, etc. If there were no mistake here, did we not 

 have to suppose that, in the body of a previously healthy person, who 

 had died neither from exhausting disease nor loss of blood, the normal 

 amount of blood was often considered pathological, these accounts 

 of post mortem would only convey the absurd idea that the entire 

 amount of blood in the body was increased by poisoning, suffocation, 

 etc. We must make it, a rule to consider hyperaemia of the cerebral 

 membranes as proved only in those cases where the finest vessels also 

 are injected, and where the overloading of the cerebral vessels is not 

 at all in proportion to the amount of blood in other organs. 



The great difficulty of detecting, in the cadaver, a hyperaemia of the 

 substance of the brain, that has existed during life, depends chiefly on 

 the fact that the first fine ramifications of the vessels supplying the 

 brain take place in the pia mater, and that the vessels passing thence 

 to the substance of the brain are mostly capillary (iMSchka). As 

 these can scarcely be recognized with the naked eye, it is customary 

 to use the size and number of the drops of blood oozing up on a cut 



