1890.] Increase of Intracranial Pressure or Tention. 273 



median and (2) a lateral part. The median part can be traced 

 horizontally backwards into the septum between the body and the 

 splenium of the corpus callosum, but not to join the cingulum as 

 described by Meynert. The lateral fibres descend the lateral 

 ventricle, becoming the teenia hippocampi or fimbria, and end in the 

 cortex of the cornu Ammonis, while the alveus of this body receives 

 fibres from its cortex, and then passes to its under surface to send 

 fibres to the inferior surface of the temporo-spheooidal lobe. Besides 

 these parts, there are the transverse fibres connecting the cornua 

 Ammonis of opposite sides. 



Particular attention is directed to the different degree of staining 

 by Weigert's method of the corpus callosum, fornix, and tsenia 

 semicircularis, of which the last is scarcely coloured, suggesting that 

 it is a degenerated or non-developed structure. 



IX. " Ou the Changes produced in the Circulation and Respira- 

 tion by Increase of the Intracranial Pressure or Tension." 

 By WALTER SPENCER, M.S., Assistant Surgeon to West- 

 minster Hospital, and VICTOR HORSLEY. B.S., F.R.S. Re- 

 ceived June 12, 1890. 



(Abstract.) 



The authors have made for some time the effect of an increase in 

 intracranial pressure or tension the subject of an experimental 

 inquiry, and they have in this paper recorded the results obtained, in 

 so far as the increase of intracranial pressure affects the circulation and 

 respiration. 



They conclude that the increase in intracranial pressure influences 

 the circulation and respiration through the diminution in the physio- 

 logical activity of the medulla which it causes, and show that the 

 changes produced by the pressure assume a sequence according to the 

 degree to which the activity of the medulla is impaired. 



The authors first give an historical resume of the work of previous 

 observers, and then a short introduction on some anatomical and 

 physiological details which relate to the part of the subject under 

 consideration. 



The method chiefly employed of increasing intracranial pressure 

 was by inserting a small rubber bag through a trephine bole in 

 the skull, and then distending the bag by means of a column of 

 mercury, which served to show at once the pressure required to dis- 

 tend the bag, and the extent to which the bag was distended. 



The capacity of the thin- walled rubber bag, when distended, was at 



