114 



Prof. J. A. Mac William. On the [Oct. 24, 



Periods of freezing insufficient to entirely obviate the appearance of 

 post-mwiem contraction may cause it to be much less pronounced. 



When a portion of artery is rapidly excised immediately after death 

 and quickly cooled to about 0° (while still uncontracted) in a suitable 

 metal vessel placed in ice for some hours, the onset of contraction is 

 usually delayed though not ultimately prevented ; in some cases its 

 development seems to be very imperfect until the artery is stimulated 

 (manipulation or cutting, &c). 



When contraction has been established for some time (e.g., a day or 

 two) cooling down nearly to 0° for some hours has no appreciable 

 effect. 



Removal of Post-mortem Contraction. 



Freezing. — An artery, however firmly it may be contracted, can be 

 made to relax by freezing it for, some hours in the way already men- 

 tioned as being effective in preventing the development of contraction. 

 The exact time required varies in different cases, but I have always 

 found 4 — 5 hours sufficient. On being allowed to thaw, the lumen 

 enlarges to the usual size of the passive artery, while its walls become 

 soft and relaxed. The contractility of the artery is completely and 

 permanently abolished. Its length is less than in the contracted 

 state. There is no apparent change in reaction of the cut surface to 

 litmus paper. 



It often seems to require a less prolonged period of freezing to 

 obviate the appearance of contraction in an uncontracted artery than 

 to remove contraction when it has been established for some little 

 time (1 hour, &c). 



Sulphocyanide. — Immersion of a contracted artery in a solution of 

 sulphocyanide of potassium soon leads to complete relaxation. When 

 a 20 per cent, solution is used, relaxation is generally found to have 

 occurred in 20 — 30 minutes, the time varying with the thickness of 

 the arterial wall, &c. Weaker solutions require longer time. Sulpho- 

 cyanide of ammonium has effects similar to the potassium salt. The 

 effect may be graphically recorded in the following way : — A strip of 

 arterial wall cut transversely to the long axis of the vessel is suspended 

 in a bath of the solution and made to pull upon a recording lever, 

 which is kept in a horizontal position by a long, feeble, spiral spring. 

 The tracing obtained shows the extensive relaxation which occurs 

 after the sulphocyanide is introduced into the beaker. A skeletal 

 muscle placed alongside the arterial strip in the bath and connected 

 with a similar lever shows a striking contrast, contracting strongly 

 under the influence of potassium sulphocyanide, as Kiihne* described 

 many years ago. Here we have the remarkable result that while 

 potassium sulphocyanide induces strong and persistent contraction in 



* ' Myologische Untersuckungen,' p. 130. 



