28 PROPERTIES OF 



EXPERIMENT X. 



I took a wide-mouthed phial, containing some serum, and 

 placing a thermometer in it, I put it into water which was 

 kept warm by a lamp underneath ; and, in making this experi- 

 ment with as much accuracy as I could, I found the heat re- 

 quired (xvn) was 160 ; which is about 40 more than is neces- 

 sary for the coagulation of the lymph. 



(xvn.) The temperature required to coagulate the serum of different 

 animals is not the same. Dr. Davy a observed a variation of 10 in the 

 coagulating point of the serum of mammals ; and it appears to vary with 

 the proportion of water in the serum, which may be indicated by its 

 specific gravity. Serum, too, first becomes opalescent and then viscid 

 at lower heats than are required to make it coagulate firmly, as I have 

 learned from experiments communicated to me by Dr. Davy, and from 

 others made by myself. He found that sheep's serum coagulated at 

 168 170, and at 172 174 when 'diluted with one third of water; 

 that common salt, magnesia, carbonate of potash, and oxalic acid had 

 very little effect on the heat required to coagulate the serum ; that its 

 coagulation was prevented, even at 212, by an excess of acetic, citric, 

 or tartaric acid ; that super-tartrate of potash promoted coagulation ; and 

 that it was retarded but not prevented by lime. Calf's serum he found 

 coagulated at 178 180; pig's serum at 158, at 180 when diluted 

 with an equal part of water, and with a sixth part of water was but 

 slightly thickened at 160. The same serum after having been kept 

 six days, but quite fresh, had its colour less readily affected by heat. 



Serum, sp. gr. 1031, gradually heated in a test-tube in water, from 

 the blood of a healthy horse, I found affected as follows : at 153 slightly 

 opalescent in reflected light ; at 155 distinctly so ; at 157 viscid ; at 

 158 a jelly, not breaking when inverted, semi-transparent in transmitted 

 light; at 164 a firm jelly, nearly opake in transmitted light; at 168 

 quite opake and very firm. Kept for above two hours at 120 130, 

 it became glairy and viscid, remaining quite transparent. Nitre had 

 little effect on the coagulation. But it was promoted by Glauber's salt ; 

 added in excess to the serum, this became white and opake at 144, and 

 curdled throughout at 146; an ounce of serum, with seventy grains of the 

 salt, kept fifteen minutes at 144, became athin semi-transparent pulp, and 

 for fifteen minutes more at 146, a feeble and quite opake jelly. Serum, 

 sp. gr. 1033, from a man aged 40, blooded for pneumonia : at Io6 

 rather opalescent in reflected light ; at 158 liquidity impaired, and after 

 forty minutes a tender jelly ; at 159 coagulated firmly after twenty-six 

 minutes, opalescent in reflected light, and quite transparent in trans- 

 mitted light; at 169, just the same : at 212 quite opake. The blood 

 was not buffy. Pellucid serum from a hydrocele, sp. gr. 1024, be- 

 came opalescent at 150; coagulated at 160; quite opake at 168. 



a Researches, Physiol. and Anat. ii, 95. 



