56 Dr. Buchanan on the State of the Blood after taking Food. 



him, Dr. R. D. Thomson found to be about three por cent. This 

 experiment appearing to me to bo an important one, I repeated it twice, 

 as will bo seen below ; and on ono of these occasions a fast of upwards 

 of twenty-four hours was rigidly observed before the meal, so as to 

 remove entirely the second objection mentioned above, and diminish 

 the first as much as I believe practicable. 



Arrow-Root— Starch and Suet.— On the 5th of July, O. and P., after a fast of 

 sixteen hours which I had no reason to suspect was not faithfully observed, had, the 

 former a mess of spiced arrow-root prepared with water, and the latter a pudding 

 composed of two parts common starch and one of suet. They were both bled im- 

 mediately before the meal, and again at two, and at four hours after it. 



The serum from the blood of O. was, the whole three times, quite transparent. 

 On testing it with salt, the serum of the blood drawn before the meal gave a preci- 

 pitate nearly as abundant as that from the blood drawn after the meal. The blood 

 taken from P. before the meal gave a scrum which was quite limpid, while the blood 

 taken after the meal gave on both occasions a very white serum : that from the first 

 bleeding after the meal threw up spontaneously a white cream, which on the third 

 day was as abundant as I had ever seen it ; that again from the second bleeding, 

 although equally white, yielded no cream. On filtering the creamy serum, the filter- 

 ing paper after being dried was found stained with oil, which it was natural to 

 think was occasioned by the suet ; but on filtering the corresponding limpid serum 

 of O., who had taken only arrow-root, the oily stain was found not less deep. The 

 serum of P. gave a precipitate with salt as well before as after the meal, and that 

 from the serum after the meal was far more abundant than could possibly have 

 proceeded merely from the matter in suspension. The serum of P. before the meal 

 was kept many days in a phial only in part filled, and yet continued quite free of 

 any unpleasant smell, both then and when afterwards poured into an open glass, 

 and allowed to remain till the water had all evaporated. I have met with several 

 other instances of serum resisting putrefaction, but can offer no probable conjecture 

 as to the cause of so remarkable a property. 



This experiment shows clearly the effect of an oily diet in giving 

 milkiness to the serum, since the milkiness was as great from the diet 

 of starch and suet just mentioned, as from the more highly azotized diet 

 of flour and suet mentioned in the last memoir. To illustrate the mode 

 in which the milkiness is occasioned, I added a few drops of oil to the 

 limpid serum of the man who had dined on the arrow-root alone, and 

 on shaking them together I found the liquid become turbid and throw 

 up a kind of cream. This effect, which I had often before observed, 

 I have been in the habit of ascribing to the action of the free alkali 

 of the serum upon the oil forming with it a kind of emulsion. There 

 are indeed good reasons for thinking that the white matter of milky 

 serum is not a mere emulsion of this kind, but an azotized substance, 

 yet it seems probable that the introduction of an oil into the blood is 

 one, and probably the most frequent cause of the white colour of the 

 serum. It is also worthy of remark, that the effect seems to be only 

 occasioned by oil recently introduced with the food, since, as in the case 

 just mentioned, we often find serum abounding witli oil, and yet quite 

 limpid, which must be owing to the oil, whether absorbed from within 

 or from without, having been so adjusted by the processes of the vital 



