;, i Prof. L. Hill. [.Tan. 25, 



ritlu-r case, the pressure required, as indicated by the mercurial 

 manometer, is the intra-cranial pressure at the time. 



4. Method* of obtaining Records of the Cerebral Venous Pressure. 

 The superior longitudinal sinus, with its tributaries, in the dog 

 opens into a large venous cavity within the occipital protuberance ; 

 the transverse sinuses lying within the bony tentorinm cerebelli lead 

 out of this cavity. Part of the blood finds its exit by the post-glenoid 

 foramen, and reaches the external jugular vein, but a very large 

 portion passes into the large sinuses which run down the vertebral 

 canal. 



The methods are as follows : 



at. A hole is drilled into the venous cavity within the occipital 

 protuberance. Into the hole a tube is fixed, filled with sodium 

 sulphate solution. The tube is connected with a water manometer. 



ft. The skull is opened over the occipital protuberance, and a 

 venous cannula passed into the superior longitudinal sinus against 

 the direction of the blood flow. The cannula is connected with a 

 water manometer. This method gives the venous pressure with 

 obstructed flow. 



In either of these methods the manometer can be connected with a 

 light and delicate tambour, and the venous pressure recorded. 



Records of the blood pressure in the carotid artery, and of the 

 respiration, were taken simultaneously with the records of intra- 

 cranial pressure. 



By the method of " worming " the trephine holes before screwing 

 in the brass tubes the connexions were made (as tested) absolutely 

 air tight. The delicacy of the measuring apparatus was tested on an 

 artificial scheme, and found to be perfect. 



Results. 



1. The normal intra-cranial pressure scarcely ever exceeds 10 ram. 

 Hg. (Method 2 and ft.) 



2. The normal cerebral venous pressure in the dog is equivalent to 

 100 120 mm. water. (Method 4 .) 



3. The pressure in the superior longitudinal sinus with the flow of 

 blood obstructed rises to double or more the normal cerebral venous 

 pressure. (Method 4 ft.) 



4. The air index in the measuring apparatus exhibits perfectly the 

 cardiac and respiratory undulations of the intra-cranial pressure. 

 (Methods 2 and 3.) 



5. The water manometer in connexion with the venous cavity in 

 the occipital protuberance, or with the longitudinal sinus, exhibits 

 the cardiac pulsations and large respiratory undulations. (Method 

 4 a and 0.) 



