EPILEPSY AND APOPLEXY. 263 



around it, and the general accumulation of blood in 

 its vessels is thus mechanically prevented. The 

 hydraulic law is, nevertheless, in full operation 

 within the cranium. The venous sinuses will have 

 a tendency to enlarge, the arterial columns will 

 still endeavour to force their way into the smaller 

 vessels, and the pressure and counter-pressure of 

 the arterial and venous blood will thus be in exist- 

 ence to the same extent, and tend to produce the 

 same general enlargement of the organ as in the 

 liver and kidneys. That enlargement being, how- 

 ever, as we have seen, a physical impossibility, the 

 distending force or pressure (which in other organs 

 produces hypera3mia or congestion) is here commu- 

 nicated laterally to the whole semi-fluid mass filling 

 the cranium, and through it to the external surface 

 of all the capillaries of the brain. But these being 

 thus compressed and flattened by the very force 

 which in health propels the blood through them, no 

 longer convey fresh streams of vitalising liquid to 

 the nervous tissues, and the functions of the latter 

 accordingly cease. According to this view, then, 

 the same distending force of the impeded columns of 

 blood, which, in other parts, leads to vascular en- 

 largement, and, through it, to an increase in the 

 bulk of the organ, is, in the brain, communicated to 

 the circumjacent pulpy mass, and thus causes an 

 external pressure which the thin membranous coats 

 of the capillaries are unable to resist. Sudden and 

 extreme irregularities in the flow of blood to and 

 from the brain are therefore capable of inducing 



the complete and simultaneous stoppage of the ca- 



s 4 



