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



incisions, branches of the pulmonary artery uncontracted and flaccid, 

 but on excising portions these speedily became contracted, so that a 

 piece of artery 4 cm. or more in length could be held out in a hori- 

 zontal position by one end. Later — 3 hours after death — deep inci- 

 sions into the lung substance showed the small arteries to be markedly 

 contracted and firm, their cut ends projecting somewhat on the sur- 

 face of the incision. Branches of the pulmonary artery 3 mm. in 

 diameter when relaxed were found to be less than 2 mm. when con- 

 tracted. 



Small branches arising from the carotid are often apparently more 

 firmly contracted than the carotid itself. 



Arteries left undisturbed in situ for 24 — 48 hours after death, and 

 then exposed, may show little sign of contraction at first, but under 

 the influence of manipulation, cutting, exposure to air, &c, may soon 

 enter into strong contraction — persisting for days. 



The importance of the presence or absence of post-mortem contraction 

 need hardly be insisted on with regard to the measurements of arteries 

 made after death to ascertain the size of lumen, the thickness of wall, 

 tunica media, &c. 



Changes in Length of Empty Excised Artery in Contraction and 

 Relaxation. 



When an empty excised artery contracts its length becomes increased, 

 and conversely on relaxing the tube shortens. Thus two portions of 

 artery (ox), measuring 25 mm. and 31 mm. in length, while strongly 

 contracted became shortened to 20 mm. and 27 mm. respectively when 

 the muscular contraction had relaxed to a great extent. 



Duration of Post-mortem Contraction. 



In the arteries of the ox and horse post-mortem contraction usually 

 lasts for several days; the usual duration of obvious contraction is 

 •about 5 or 6 days, when the artery is kept in an ordinary room. In a 

 warm room contraction passes off' earlier, and in a cool room its dura- 

 tion is considerably prolonged. When placed in a warm chamber (in 

 •defibrinated blood) at about 40° C, the contracted artery is found to 

 become completely relaxed in 24 hours or less ; its walls become 

 flaccid, and its lumen enlarges from a diameter of perhaps 2 or 

 ■3 mm. to one of 5 or 6 mm. Subsequent stimulation (mechanical, 

 chemical, electrical, &c), cooling, and exposure to air, entirely fail 

 to induce any contraction. There is no evident change in reaction 

 to litmus paper. 



Immersion in olive oil exercises a powerful influence in prolonging 

 the duration of post-mortem contraction. In the carotid of the horse so 

 treated I have seen an appreciable amount of contraction present as 



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