110 



Prof. J. A. MacWilliam. On the 



[Oct. 24, 



often be held out (by one end) in an almost horizontal position. These 

 changes may be seen 10 — 15 minutes after death or many hours later ; 

 they occur in all systemic and pulmonary arteries that have well- 

 developed muscular coats. An artery excised shortly after death may 

 be strongly and persistently contracted long before rigor mortis has 

 appeared in the heart or skeletal muscles, and indeed while these 

 muscles are still obviously living. 



Causes of Post-mortem Contraction. 



(1.)- Mechanical stimulation has a powerful influence, e.g. f cutting, 

 manipulation, &c. When an artery is cut across, contraction begins 

 at the cut, and thence spreads along the tube more or less completely ; 

 an excised piece of artery some inches long often shows very well- 

 marked contraction near both ends, while the middle part may be 

 relatively soft and relaxed ; an incision made in this middle part 

 speedily induces marked contraction there also. 



Pieces of excised artery show considerable variation in the extent to 

 which the contraction excited at the cut ends involves the intermediate 

 portion of the tube. 



(2.) Cooling to a few degrees above zero favours the development of 

 contraction in an exposed artery. Warming a contracted (cold) artery 

 up to about 40° very commonly has a markedly relaxing effect, though 

 the relaxation is usually incomplete ; a piece of contracted artery put 

 into defibrinated blood and kept in a warm chamber for an hour or so 

 usually relaxes to a considerable extent — at least, if the experiment is 

 done within a day or so after death, the artery being excised shortly 

 after death ; it may again contract very markedly when the tempera- 

 ture falls. 



(3.) Exposure to the air also seems to play a part in inducing and 

 favouring post-mortem contraction.* 



When a piece of artery is excised as speedily as possible after death 

 and at once immersed in olive oil while still flaccid, and kept in the 

 oil, post-mortem contraction is, as a rule, much less strongly marked, 

 though it may be extremely long-continued. 



Again, when a relaxed artery is exposed immediately after death 

 and covered over with olive oil, cutting into the arterial tube while it 

 is immersed in oil causes, as a rule, a decidedly less pronounced con- 

 traction than usual. 



Post-mortem contraction is well marked in all arteries, pulmonic as well 

 as systemic. 



In the lungs of an ox an hour after death I found, on making deep 



* In the case of a living artery in situ (posterior tibial), Jolin Hunter observed 

 that the vessel contracted very much on being exposed to the air for some time. 

 Cooling may possibly have played some part here. ' Works ' (London, 1837), vol. 3, 

 p. 157. 



