1906.] Obstruction of the Venm Cavce and the Portal Vein. 269 



4. Effects of obstruction of the portal vein : — 



(a) Upon the production of dropsy. 



(b) Upon the circulation of the blood. 



5. Effects of obstruction of the superior, together with the inferior, vena- 



cava : — 



i (a) Upon the production of dropsy. 



(b) Upon the circulation of the blood. 



6. Production of hydremic plethora after obstruction of the inferior vena 



cava. 



7. Conclusions. 



1. Method. 



The animals used were cats. The anaesthetic in all cases was ether, and 

 morphia was administered in addition in those experiments relating to the 

 effects upon the blood-pressures. 



In order to obtain access to the superior and inferior venae cavae, the chest 

 was opened by an incision an inch or more long and parallel to the ribs in the 

 third right intercostal space in the case of the superior, and in the seventh 

 right space in the case of the inferior vena cava. The ribs were drawn apart 

 by weighted retractors and the lung held aside by a small copper spatula. 



If the vein were to be completely obstructed, it was ligatured with silk ; if 

 incompletely obstructed, a piece of Jacques' rubber catheter of the appropriate 

 diameter and about \ inch in length was placed round the vein and tied on.. 



In those experiments, which were done in order to determine, by a gradually 

 increasing constriction, at what point the venous or arterial pressure was first 

 altered, a fine wire was passed round the vein and the free ends of this wire 

 pushed through a piece of glass tubing so as to form a snare. The loop so 

 formed was gradually tightened until an effect was observed upon the blood- 

 pressure ; the vein was then cut through and the wire loop removed and its 

 diameter measured. 



In all cases during the operation, artificial respiration was maintained 

 through a tracheotomy tube if the animal were to be killed at the end of the 

 experiment ; but if it were to be allowed to live, a piece of glass tubing was- 

 introduced into the larynx through the mouth and artificial respiration 

 maintained in this way, the air being blown through a bottle containing ether. 

 Strict antiseptic precautions were observed and a post-mortem bacteriological 

 examination made in most of the cases. 



No difficulty with regard to pneumothorax was experienced after the chest 

 was stitched up, and the animals began to breathe naturally at once. 



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