Brain and the Conditions of Recovery after Compression. 1 7 



To render this part of the paper more comprehensible, it is neces- 

 sary to give a short description of the vessels providing for the 

 outflow of blood from the dog's skull, as their anatomy presents 

 many points of difference from that of the human being. The 

 details are chiefly as stated by Ellenberger and Baum.* 



The greater part of the venous blood leaves the skull through the 

 foramen magnum by route of the inferior occipital sinuses, and enters 

 the venous plexus of the vertebral column. 



The vein next in individual importance is the superior cerebral, 

 which finds exit from a foramen situated, on either side, between the 

 post-glenoid protuberance and the external auditory meatus. It 

 communicates, through the medium of the meatus temporalis, with 

 the lateral sinus of its own side. It is often of considerable size, and 

 is one of the chief sources of the internal maxillary vein. 



The internal jugular receives, along with other branches, the 

 inferior cerebral vein, which runs in the carotid canal and opens into 

 the cavernous sinus. 



The internal jugular is very small, and carries away but little 

 cerebral blood. 



Running through the orbital fissures are important veins (oph- 

 thalmo-cerebral and cerebro-facial), which connect the cavernous 

 sinuses with the external maxillary veins. 



In addition to these, there are numerous emissary veins, and 

 between all the channels of exit named there is free anastomosis. 



(6.) Method of Experiment. I exposed the accessible cranial veins, 

 viz., the external and internal jugulars, and internal maxillaries ; the 

 latter I followed nearly to their termination in the superior cerebrals. 

 I then blocked the various veins in succession by clamps, and per- 

 formed the usual experiment upon the congested brain. 



To make the experiments more complete in one case, I measured 

 the change in the venous pressure in the lateral sinus by means of a 

 cannula inserted into one superior cerebral vein and connected with 

 a water manometer. Directions for dissecting out this vein are given 

 by Gartner and Wagner ,f but I always found it necessary to remove 

 the angle of the lower jaw in addition. 



In the following table I have noted the degree of elevation of the 

 brain surface, denoting the amount of congestion following blocking 

 of the main venous outlets. 



* ' Anatomic des Hundes.' 



t Wagner and Gartner, ' Med. Wochenschrift,' Wien, 1887, Nos. 19 and 20. 

 VOL. LVIII. C 



