130 



Prof. J. A. MacWilliam. On the [Oct. 24, 



MgS0 4 or NH4CI extract when heated with those occurring within 

 the tissues of the arterial wall in the following way : — Weighed 

 amounts of the arterial wall were taken and heated at the usual rate 

 up to various temperatures (40°, 45°, 50°, 55°, 60°, &c), immersed in 

 mercury contained in small (corked) test-tubes, which were placed in 

 the oil-bath. The portions of artery so treated were then extracted 

 with equal amounts of 5 per cent. MgS0 4 or 13 per cent. NH 4 C1 

 solution for equal periods, for comparison with portions of the same 

 artery which had not been heated at all. The different extracts were 

 tested for the amount of proteid which they contained by heat-coagu- 

 lation, precipitation by various reagents, &c. 



It was found that heating fresh artery up to 40° or 45° made no 

 appreciable difference in the amount of proteid subsequently obtain- 

 able from it by 5 per cent. MgS0 4 sol., while heating to 49° or 50° 

 markedly diminished the subsequent yield of proteid. Obviously a 

 considerable amount of proteid has been rendered insoluble at 45 — 50° 

 in the tissue. Heating to 55° did not seem to make any marked 

 difference as compared with heating to 50°. A temperature of 60° 

 caused the subsequent yield of proteid to be greatly lessened ; indeed 

 there was little extracted by the MgS0 4 sol. after the artery had 

 been heated to 60°. Evidently coagulation had taken place between 

 55° and 60°. 



Comparing these results with what is seen on heating the acidulated 

 MgS0 4 extract of an artery that has not been heated, we find that 

 proteid is rendered insoluble in the tissue of the arterial wall at about 

 the same temperatures as in the extract. In the case of the non- 

 acidulated extract, proteid becomes insoluble in the tissue (45 — 50°) 

 when the extract becomes strongly opalescent, but shows no floccules 

 capable of separation by filtration • later (55 — 60°) proteid is rendered 

 insoluble at a somewhat lower temperature than is usually required 

 to give a flocculent heat-coagulum (60 — 65°) in the non-acidulated 

 extract. 



Changes in the length of strips of the arterial wall bear a relation 

 to the coagulation of proteid in the tissue similar to what has already 

 been stated in regard to MgS0 4 extracts, excepting that the rendering 

 insoluble of proteid at 55 — 60° in the tissue comes distinctly before 

 the final shortening of the strip. 



Saline Extracts of Relaxed Artery. 



Some of the methods already described as effective in relaxing a con- 

 tracted artery would obviously render the subsequent making of saline 

 extracts impracticable (sulphocyanide, &c). 



The freezing method is not open to this objection. Extracts made 

 with 5 per cent. MgS0 4 from an artery relaxed in this way show heat 



