Dr. Buchanan on the State of the Blood after talcing Food. 63 



former a few globules were seen with the microscope ; in the latter numerous irre- 

 gular particles. On adding as much salt as it could dissolve to the former, it 

 immediately became quite opaque, and showed large flocculent white masses floating 

 through it, which, however, had no tendency to ascend, and at length fell to the 

 bottom. But for this last circumstance, the appearances would have been very 

 much the same as are observed on adding water to an alcoholic solution of Cam- 

 phor. The other specimen of serum was treated in the same way, with a similar 

 result, only the flocculent precipitate was much less abundant. 



The coagulum of the blood first drawn had a fibrinous crust : that of the last 

 -Iniun none. 



Two conclusions may bo drawn from these last experiments: first, 

 that the effect of the salt is not merely mechanical, but a true chemical 

 precipitation ; and, second, that the white matter proceeding from dif- 

 ferent kinds of food is probably not always the same, since in some 

 cases it seeks the bottom, and in some the top. Subsequent trials 

 tended to confirm both these conclusions. 



As this is the first time I have had occasion to mention the 

 action of salt in causing precipitation from serum, I shall here explain 

 the mode in which the salt requires to bo employed: as the process 

 will thus be more readily comprehended, than if I left the knowledge 

 of it to be gleaned in the way I myself learned it, from the experiments 

 to bo hereafter mentioned. 



In the former memoir I described the action of salt in separating 

 the white matter of milky serum to be purely mechanical, increasing 

 the specific gravity of the liquid, and thus causing the solid particles 

 diffused through it to rise to the surface. This I still believe to be 

 the true mode of action of the salt, whenever it is added in less 

 quantity than the serum is capable of dissolving; but no sooner is the 

 salt added to saturation than it acts in a totally different way, and 

 becomes a true chemical precipitant. This I was led to find out from 

 my having adopted it as a consequence of the mechanical theory 

 above stated, that the heavier the serum was made the more readily 

 would the separation of the white matter take place ; and expecting on 

 this principle to obtain at once a maximum effect, I added the salt 

 till a portion of it remained at the bottom undissolved. Operating 

 thus, I was surprised to observe the great increase in the quantity of 

 the white product, which, as stated above, was much greater than 

 could have been anticipated from the whiteness of the serum, and I 

 even found afterwards that it could be obtained in as great abundance 

 from serum which was perfectly limpid. I was thus assured that the 

 salt added to saturation did not act in a mechanical way, but acted as 

 a true chemical precipitant 



To the white substance thus obtained I gave, provisionally, the name 

 of Pabulin; on the supposition that it proceeds from the alimentary 

 matter or pabulum, which has just undergone digestion in the first 

 passages. This namo will accordingly be employed below to designate 

 the white substanco obtained from the blood by the process just 



