1901.] Properties of the Arterial and Venous Walls. 



131 



coagulation (when acidulated) at 45 — 50° and 55 — 60° * also arteries 

 that have been kept for days until contraction has passed off, and 

 arteries relaxed by keeping at body temperature for 24 hours, &c. 



Now strips from such arteries — if completely relaxed — show no 

 important change when heated until the 60 — 65° shortening takes 

 place ; there is no alteration in the tracing coincident with the heat- 

 coagulations at 45 — 50° and at 55 — 60°, which are seen in the MgS0 4 

 extract. 



Saline Extracts of Aorta and Pulmonary Artery. 



These when acidulated and heated show relatively little proteid 

 coagulation, as might be expected from the relatively small amount of 

 muscle in their walls ; the temperatures of coagulation seem to be pretty 

 similar to those of extracts of carotid. 



Contraction v. Rigor Mortis. 



Is the post-mortem contraction seen in an artery a true contraction of 

 exceedingly long duration, or is it a condition of the same nature as 

 the rigor mortis of skeletal muscle 1 



There is a variety of evidence in favour of the conclusion that post- 

 moiiem contraction of arteries is a true persistent contraction, very 

 different in many respects from the rigor mortis of skeletal muscle. 



(1) As has been already stated, though the excised artery goes into 

 the contracted state very soon after death, its excitability may be 

 maintained for two or three days. Up to this time then it is obvious 

 that the arterial contraction has been of a nature very different from 

 true rigor mortis. The same is indicated by the partial relaxation 

 of the contracted artery, which may spontaneously develop a day 

 or two after death — to be followed by further contraction of the 

 application of a suitable stimulus. The reaction of the cut surface to 

 litmus paper is alkaline or amphoteric, even after the contraction has 

 lasted for days. 



(2) The effect of sulphocyanide of potassium solution applied to a 

 contracted artery is strikingly different from what is seen in the case of 

 a skeletal muscle contracted in rigor mortis. The artery, as has 

 already been described, soon becomes completely relaxed in the solution, 

 whereas the rigor mortis muscle does not relax at all. 



(3) The influence of freezing for some hours is very different in the 

 two cases. In the artery freezing quickly after the death of the 

 animal, before post-mortem contraction has begun, entirely prevents the 

 appearance of that contraction ; in skeletal muscle similar freezing does 

 not obviate the subsequent development of rigor mortis (with acid 

 reaction, &c). Portions of skeletal muscle from the ox, horse, &c, 

 were frozen for four hours, and showed a marked contrast to arteries 



