1902.] Properties of the Arterial and Venous Walls. 109 



support may have sufficed to render the atmosphere within the flask 

 conducting. And in the later experiments of the same observer, the 

 phosphoric anhydride used as drying agent may have contributed an 

 acid impurity. Sir Wm. Crookes has recently given an illustration of 

 the manne? in which impurities may be derived from phosphoric 

 anhydride. By heating it strongly in vacuo, he got rid of these to 

 such an extent that they were no longer recognisable by the spectro- 

 scope ; but it cannot be supposed that even such treatment suffices to 

 render the anhydride innocuous, bearing in mind the extraordinary 

 delicacy of the electroscopic test. 



I venture to think that until the phenomena of conductivity pre- 

 sented by gases have been studied not merely with the same, but even 

 with far greater, care than has been devoted to the study of those 

 attending gross chemical changes in gases, it is premature to conclude 

 that gases undergo ionisation — using the word in its modern sense. 

 I also venture to think that the question whether mere molecules 

 cannot form conducting systems has not yet received in any way the 

 attention it deserves from those engaged in these inquiries. 



" On the Properties of the Arterial and Venous Walls."* By 

 J. A. Mac William, M.D., Eegius Professor of Physiology in 

 the University of Aberdeen. Communicated by Sir M. Foster., 

 Sec. RS. Received October 24,— Bead November 28, 1901. 



(From the Physiological Laboratory of the University of Aberdeen.) 



Post-mortem Contraction of Arteries. 



So long ago as 1891 I noticed that the excised carotid artery of a 

 recently-killed ox exhibits a strongly-marked and long-persisting con- 

 traction of its muscular wall. The phenomenon is, of course, most 

 easily studied in the arteries of the larger animals. In this investiga- 

 tion I have examined arteries from thirty-five oxen and a considerable 

 number of horses, sheep, cats, and men. 



When the carotid of the ox or horse is exposed immediately after 

 death, it is found to be soft and flaccid, and more or less flattened in 

 section, with a large bore, usually 5 — 6 mm. On exposure to the 

 air, cooling, manipulation, cutting, &c, the artery speedily becomes 

 rigid and contracted ; the tube becomes circular in section, and its 

 calibre is greatly reduced, e.g., to an internal diameter of 2 — 3 mm., or 

 less. The artery becomes so stiff that a piece 7 or . 8 cm. long may 



* A statement of the chief conclusions arrived at in this investigation was com- 

 municated to the Physiological Society (at Edinburgh) on July 20, 1901. 

 VOL. LXX. I 



