ii6 



Scientific Proceedings (38). 



external jugular veins of the recipient and the central end of a 

 similar vein in the donor, omitting the opening of the vein in the 

 left side of the recipient's neck. This prevents the early termi- 

 nation of the experiment by the exsanguination of the donor. 1 



By this procedure, the arterial supply of the recipient's head 

 and neck is maintained through the right vertebral and left com- 

 mon carotid arteries, both of which are branches of the brachio- 

 cephalic artery. The venous outflow is maintained by the unob- 

 structed passage of the blood into the superior vena cava from 

 which it escapes through the external jugular vein on the right or 

 left side as the case may be. 



Injections may be made into the cerebral circulation of the 

 recipient through a hypodermic needle inserted in the carotid 

 artery in the region of anastomososis, or through a canula placed 

 in the central end (clamped) of the superior thyroid artery. It is 

 also evident that the solution may be given intravenously in the 

 donor, but under such circumstances the influence of changes in 

 the arterial blood pressure of the donor must be considered. 



By this method of isolation, physiological experimentation 

 upon altered cerebral blood pressure is rendered feasible by (1) 

 diminishing the venous outflow through the jugular anastomosis, 

 (2) by constriction of the arterial anastomosis, or (3) by raising the 

 donor's general blood pressure. 



The success of this method of isolation is evidenced by the fact 

 that an injection of horse serum into the cerebral circulation of a sen- 

 sitized animal does not cause the typical fall of blood pressure which 

 is characteristic of anaphylactic shock, while a subsequent injection 

 into the trunk does cause such a fall. 



73 (483) 



A reversion of the starch- dextrin reaction. 

 By EDWARD TYSON REICHERT. 



[From the S. Weir Mitchell Laboratory of Physiology, University 

 of Pennsylvania.] 

 In the reversions of enzymic and catalytic processes heretofore 

 recorded, the synthesis has been brought about by a high concen- 



1 Before making the venous anastomosis it is essential to ascertain whether there 

 is an efficient back flow from the superior vena cava through the central end of the 

 recipient's right external jugular vein. To provide this it is frequently necessary to 

 rupture the valves that are present just above the subclavian branch. 



