PARTIAL ANJ3MIA OF THE BRAIN. 213 



on the space, do not entirely compress the capillaries of the affected 

 hemisphere, so that they do not cause hemiplegia, or at least it is only 

 slight, while the propagation of pressure to the other hemisphere is 

 shown by psychical disturbances, which are usually absent where the 

 affection is limited to one side of the brain. Perhaps this may partly 

 explain the aphasia, which is found with disease of the frontal lobe of 

 one side, particularly (but not constantly) of the left side ; since, in 

 the region of the frontal lobes, pressure acting on one side is very 

 readily propagated to the other. As the two sides of the brain are so 

 symmetrical, it is difficult to believe that there is any organ in one 

 which does not exist in the other. 



Even more characteristic and more constant is the combination of 

 symptoms accompanying compression of the capillaries of the parts of 

 brain in the posterior cranial fossa. This is apparently because the 

 tentorium can offer greater resistance to pressure acting on it than the 

 falx can ; also because the communication from the posterior and lower 

 chamber of the skull, bounded by the tentorium and occipital bone, 

 with the upper chambers, is far less free than that which exists be- 

 tween the two upper chambers. As is well known, we may readily 

 err in diagnosis of diseases of the brain, but I do not remember to 

 have made a mistake when I have given a diagnosis of disease con- 

 tracting the space in the posterior cranial fossa. Many of my former 

 pupils also have assured me that, from experience in their own practice, 

 they must regard the diagnosis of diseases limiting the space in the 

 posterior cranial fossa as easy, and that they have repeatedly diag- 

 nosed them according to my instructions, and have verified the diag- 

 nosis by autopsy. The combination of symptoms from which we may 

 diagnose compression of the capillaries of the parts lying in the pos- 

 terior cranial fossa is as follows : Pains in the back of the head, sym- 

 pathetic vomiting, a peculiar dizziness, diminution of sensibility and 

 motor power, but no complete paralysis and anaesthesia regularly 

 spread over the body, and impaired articulation and deglutition. The 

 pains at the back of the head doubtless proceed from the filaments of 

 the trigeminus going to the tentorium. As the sympathetic vomiting 

 occurs in various brain-diseases, it alone has no diagnostic value, but, 

 in combination with other symptoms, it greatly aids to render the pic- 

 ture of the disease characteristic. The dizziness accompanying dis 

 eases contracting the space in the posterior cranial fossa is not a hallu- 

 cination, a subjective sensation of movement of the patient's own body, 

 Dr of surrounding objects, that does not really take place. Unlike 

 this far more frequent hallucinatory form of dizziness, it does not occur 

 while the patient is quietly lying or sitting down, but results from 

 certain bodily movements. When a patient complains of dizziness, 



