101 Mr. W. D. HaUiburton. [June 19, 



in altering the temperature up to a certain limit, the greater the 

 excess of acid present the lower being the temperature of coagulation. 

 A series of experiments to define precisely what this relation is is at 

 present in progress. The serum of several animals has been 

 examined, viz., the ox, sheep, horse, dog, rabbit, pig, cat, monkey, 

 man. The plasma of two of these animals, viz., the dog and monkey, 

 were also examined, and gave confirmatory results. 



The experiments relating to the plasma and serum of the dog will 

 now be detailed at greater length, as an illustration of the method 

 used. 



1. A portion of plasma, prevented from coagulating by the addition 

 of sodium sulphate, was rendered faintly acid, and a.t the following 

 points coagulation occurred : 



56 C. White floccnlent precipitate ; filtered off ; filtrate faintly 



alkaline ; it was rendered faintly acid, and heated to 

 73 C., when a dense floccnlent precipitate occurred. This was 



filtered off ; the filtrate, again alkaline, was rendered 



acid, and heated to 

 75 C., when a small amount of a finely divided precipitate 



occurred ; from the filtrate, after this always rendered 



faintly acid, coagula separated at 

 77 C. and 



82 C. After filtering off this last precipitate, the filtrate was found 

 to be free from proteid. 



2. A portion of plasma was saturated with powdered magnesium 

 sulphate; a precipitate was so obtained which Hammarsten has 

 shown to consist of globulin. This was filtered off", and the filtrate 

 then treated as the original plasma ; at the points 73 C., 77 C., and 

 82 C., white flocculent precipitates were found to occur. The preci- 

 pitate caused by magnesium sulphate was washed with saturated 

 solution of magnesium sulphate, and then dissolved by adding distilled 

 water. An opalescent solution was so obtained, and by the process 

 of fractional heat-coagulation precipitates were found to occur at 

 56 and 75 ; the filtrate after the latter containing no proteid. 



3. After heating another portion of plasma to 75 C., and filtering 

 off the coagulum, magnesium sulphate produced no precipitate, 

 showing that all the globulins went down at or below 75 C. 



4. With the serum of the same animal, the dog, treated in a similar 

 manner, the following are the points at which coagula appeared : 

 70, 75, 77, and 8283. 



5. With another portion of serum, to which saturated solution of 

 sodium sulphate had been added, in the same proportions in which it 

 had been added to the plasma to prevent coagulation, the points at 

 which coagula fell were 73, 75, 77, and 83. 



