1901.] Properties of the Arterial and Venous Walls. 129 



Neutral Extract. 



The fluid became strongly opalescent at 45 — 50°, but as a rule did 

 not become flocculent, and no precipitate could be separated by filtra- 

 tion. (Compare Vincent and Lewis's results with non-striped muscle 

 from the stomach of the calf • these authors remark a similar absence 

 of definite coagulation in neutral extracts.*) 



Well-marked coagulation became evident at 60 — 65° as a rule. 



Saturation with MgS0 4 appeared to precipitate nearly all the 

 proteid contained in the saline extract. Shaking was not employed 

 in effecting saturation ; the extract was allowed to stand for 24 hours 

 with excess of MgS0 4 crystals, and inverted from time to time. 



Small test-tubes, containing 5 per cent. MgS0 4 extract of the 

 arterial wall (neutral or acidulated), were often placed in the oil-bath, 

 in which strips of the same artery were being heated and made to 

 record their changes in length ; the changes in the strips and the 

 MgS0 4 extract placed side by side under the same conditions were 

 compared. 



Contracted Artery. 



The early contraction frequently occurring (25 — 35°) in the strip 

 was attended by no evident change in the MgS0 4 extract, nor was the 

 relaxation about 40°. The contraction frequently seen between 45° 

 and 50°, especially about 47°, coincides with the development of 

 marked opalescence in the neutral MgS0 4 extract, and with coagula- 

 tion in the acidulated extract. 



The characteristic relaxation at 50 — 55° follows upon the change in 

 the MgS0 4 extract just mentioned, and corresponds with no definite 

 further change in that liquid. 



The final shortening of the strip at about 65° takes place pretty 

 much at the same time as coagulation in the extract, but evidently 

 does not essentially depend on that coagulation, since it occurs in 

 strips that have been macerated for many days in large quantities of 

 13 per cent. NH 4 C1 solutions. 



When an acidulated MgS0 4 extract is used to compare with the 

 changes occurring in the heated strip, the preliminary precipitation 

 caused by the addition of a little 2 per cent, acetic acid has to be 

 borne in mind. For the substance thus precipitated and removed by 

 filtration might possibly have been one which would have shown a 

 change in relation to some of the phases in the behaviour of the arterial 

 strip during heating. 



Of course this objection does not apply when a non-acidulated 

 MgS0 4 extract is used in making the comparison. 



An attempt was made to co-ordinate the changes occurring in a 



* 'Journal of Physiology,' vol. 26, p. 445. 



