1901.] Properties of the Arterial and Venous Walls. 113 



Even so long as 4 days after death the carotid of a horse was seen 

 to contract from a diameter of 5 mm. to one of 3 mm. 



Suprarenal extract has a marked influence in inducing arterial con- 

 traction even at relatively long periods after the death of the animal, 

 e.g., 24 — 48 hours, or longer. An excised portion of artery placed 

 in a watery decoction (made with normal saline) of suprarenal medulla 

 speedily goes into strong contraction, persisting for a day or two ; 

 at length the contraction passes off. As might be expected the con- 

 traction is excited more effectively in a relatively thin-walled artery 

 like the carotid of the sheep than in the thick-walled artery of the ox 

 or horse. Decoctions of suprarenal medulla made with tap water, as 

 well as with normal saline, were tried. 



It is to be noted that both tap-water and normal saline, by them- 

 selves, have a very appreciable effect in inducing contraction in an 

 artery for some time after death*. But these effects are much more 

 transient than those produced by suprarenal extract ; the contraction 

 following the application of normal saline or water commonly passes 

 off within 2 or 3 hours, while that induced by suprarenal extract 

 is usually well marked till the following day or even later. 



When a certain period, varying • according to circumstances, has 

 elapsed after death, an excised artery, though still showing marked 

 contraction, fails to respond appreciably to any form of stimulation. 



Prevention of Post-mortem Contraction (by Freezing). 



Freezing a piece of artery immediately after excision from a 

 recently-killed animal prevents the development of contraction 

 .altogether if the artery be taken out speedily while still flaccid and 

 ■at once frozen for a sufficient time. When the artery is at length 

 allowed to thaw it remains permanently relaxed, with large bore 

 (5 — 6 mm). To bring about this result, 4 hours' freezing suffices in 

 all cases ; very often much shorter periods (J, 1, 2, 3 hours) are enough. 

 In these experiments care must be taken to prevent any of the 

 mixture gaining access to the artery. Arteries so treated respond to 

 no form of stimulation. There seems to be no appreciable change in 

 the reaction of the cut surface of an artery (to litmus paper) after 

 freezing. 



There is some evidence tending to show that pieces of artery taken 

 very early after death may be prevented from going into contraction 

 by shorter periods of freezing (e.g., 30 min., &c.) than is necessary 

 with pieces taken later. 



Freezing one end of a segment of uncontracted artery (excised im- 

 mediately after death) for some hours causes that end to remain large 

 in calibre and relatively flaccid, while the other end which has not 

 been frozen goes into marked contraction and usually remains con- 

 tracted for days. 



