1888-89.] Haycraft and Duggan on Coagulation by Heat. 379 
Statement as to whether it is possible to speak of the Specific 
Coagulation Point of an Albumen. 
From what has been already said, it is obvious that it is a 
difficult and perhaps a valueless task to attempt to determine what 
may be termed the “ specific coagulation point ” of an albumen. 
The coagulation point varies with the rapidity of heating, 
with the concentration of the fluid, with its reaction, and with 
the saline substances present. All that one can say is that, 
under such and such conditions, an albumen coagulates at such 
a temperature. It is probably hardly possible to obtain even 
two albumens under such similar conditions that their coagu- 
lation points may with advantage be compared. The nearest 
approach to this would perhaps be to dissolve a certain weight, say 
both of vitellin and another globulin such as serum globulin, in 
the same volume of salt solution. The coagulation points may, 
in this case, with advantage be compared. But what would be 
the value of the coagulation points so obtained for purposes of 
comparison with serum or egg albumen dissolved in water? The 
coagulation points quoted by previous writers cannot be taken in 
any sense as absolute values for the albumen named, modifying 
conditions having, as a rule, been totally disregarded. The same 
may be said of our own results, for the percentage strengths of the 
albuminous solutions used by us were in no case determined with 
any care. Although the forms of the curves represented in the 
charts are not affected by this, their altitudes in the scale of 
temperatures may be so to some, considerable extent. 
On so-called Fractional Coagulation. 
So far we have been dealing with albumen in its natural condition, 
or mixed and possibly combined with neutral salts which we had 
added. 
The solutions were alkaline, and, as we found, when dealing with 
the natural albuminous solution, difficult to coagulate, especially if 
in a dilute condition. Let us now consider the coagulation point 
of an albuminous solution to which an acid has been added. On 
adding an acid to an albumen solution, the coagulation is rendered, 
as every one knows, more easy, and it occurs at a lower temperature. 
The very dilute solutions, uncoagulable in the alkaline solution, 
