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



lengthens again during cooling, so that it returns to the same, or 

 almost the same, length as it was at first. (Fig. 11.) 



Fig. 11. — Upper tracing, jugular vein; lower, carotid. Transverse strips, heated 

 up to 40° and then allowed to cool. 



Saline Extracts of Contracted Artery. 



Saline extracts of the fresh arterial wall were made from the 

 carotid, &c, usually with 5 per cent. MgS0 4 solution ; 10 per cent. 

 NaCl and 13 per cent. NH 4 C1 were occasionally employed. The outer 

 and inner coats were often stripped off as completely as possible, so 

 that little more than the tunica media was used. 



The 5 per cent. MgS0 4 extract is usually neutral. 



It was heated up gradually by Halliburton's method, sometimes 

 without acidulation, sometimes faintly acidulated with 2 per cent, 

 acetic acid. The rise of temperature was commonly about the rate of 

 1° C. per minute, though this was made to vary widely, and the fluid 

 was often kept at certain temperatures for many minutes. 



Acidulated Extract. 



Coagulation occurred between 45° and 50°, usually about 47°. 

 When this was filtered off and the heating continued, a second coagu- 

 lation took place at 55 — 60° — figures corresponding with the coagula- 

 tion temperatures of Halliburton's paramyosinogen and myosinogen. 



(There was some evidence of a further slight coagulation at about 

 72 — 75°.) The amount of coagulation occurring at 45 — 50° and at 

 55 — 60° varied very markedly ; sometimes the one and sometimes the 

 other predominated. It is to be noted that when the preliminary 

 acidulation is done a certain amount of precipitation occurs — probably 

 nucleo-proteid, in part at least. After filtration, the liquid is treated 

 as above described. 



