148 



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



This is a point of considerable significance and favours the view that 

 the post-mortem contraction is a true persistent contraction, and not of 

 the same nature as the rigor mortis of skeletal muscle. 



The carotid of the sheep gave results essentially similar to those 

 obtained from the ox, as is shown in the following figures. The 

 graduated tube of the plethysmograph was of 1 mm. calibre; the 

 expansion is expressed as before by the movement of the oil— stated in 

 millimetres. 



Pressure.— 20 40 60 80 100 120 140 160 180 200. 

 220 240 260. 



Expansion.— 4 5 10 14 21 26 28 30 42 45 55 65 80. 



Another sheep's carotid with less strongly-marked contraction showed 

 the maximum expansion at 100 — 120. 



Pressure.— 20 40 60 80 100 120 140 160 180. 

 Expansion.— 4 4 710 13 16 14 14 12. 



A portion of the same artery when kept for some days in blood 

 showed only slight evidence of contraction ; its maximum distensibility 

 was found to be between 40 and 60 mm. The artery was very much 

 more distensible at low pressures. 



Pressure.— 20 40 60 80 100 120 140 160 180 

 200 220 240 260 280 300 320 340 360 

 380 400. 



Expansion.— 17 32 50 42 29 20 12 10 8 7 6 



5 5 5 4 4 3 4 3-5 3-5. 



Roy's well-known conclusion that the maximum distensibility of an 

 artery was found at pressures corresponding, more or less exactly, to 

 their normal blood-pressure, was probably based on the fact that he 

 was dealing (unwittingly) with arteries in post-mortem contraction. 



As regards the arteries in diseased animals and persons, Roy 

 found that when defective nutrition, marasmus, &c, had been well- 

 marked before death the arteries were found to be wider than normal, 

 and their maximum distensibility was reached at pressures below 

 normal — in some instances coming immediately above zero pressure. 



Here there is good reason to believe that post-mortem contraction was 

 small in amount or absent. I find that in emaciated worn-out old 

 horses, post-mortem contraction is commonly very much less strongly 

 developed than in more vigorous horses ; and notably less so than in 

 healthy oxen. In cases of exhausting disease in man there is 

 reason to believe that post-mortem contraction is very slight in amount 

 or absent. 



