322 Dr. R. D. Thomson on the Digestion of 



nuation of my researches on electro-physiology, — on the sub- 

 ject of which I hope soon to be able to address the Royal 

 Society, — I have not been able to continue the study of this 

 phsenomenon. 



If you think it worth it, give this letter to Mr. Taylor for 

 the Philosophical Magazine. 



Yours faithfully, 



Pisa, March 7, 1846. Carlo Matteucci. 



XLVIII. On the Digestion of Vegetable Albumen^ Fat and 

 Starch. By Robert D. Thomson, M.D.j Lecturer on 

 Practical Chemistry in the University of Glasgow^. 



T\IGESTION of Vegetable Albumen and ivz/.— Nearly three 

 years ago Dr. A. Buchanan communicated to me the 

 fact, that he had frequently observed the serum of the blood 

 to present a white appearance when a person happened to 

 have been bled for some affection of such a circumscribed na- 

 ture as not to interfere with the appetite or digestion ; but an 

 opportunity did not occur to me of examining this peculiar 

 serum till the end of 1843, when Dr. Buchanan was so kind 

 as to place some of it at my disposal. The fluid presented 

 the appearance of thin milk, being covered, after standing, on 

 the upper surface with a whitish scum of a denser character 

 than that which was diffused through the fluid. When the 

 fluid was filtered a portion of the scum remained on the filter 

 while the liquid passed through, possessing still a milky aspect, 

 but obviously being deprived of a considerable portion of its 

 denser particles. Dr. Buchanan however observed that this 

 white matter might be accumulated in larger quantities, or at 

 least collected into smaller bulk, by saturating the serum with 

 common salt, when the white matter speedily rose to the sur- 

 face in the form of a creamy layer, which did not change its 

 physical character even when kept for monthsf. I found that 

 the white matter, both when separated simply by the filter and 

 also when precipitated, if we may so speak, by common salt, 

 contained a substance which was insoluble in eether and al- 

 cohol, and that when dissolved in caustic potash and the so- 

 lution was boiled with acetate of lead, a black precipitate of 

 sulphuret of lead fell J. These experiments were several 

 times repeated carefully with the same result, and were wit- 

 nessed by Dr. Buchanan, so that we had no doubt in our own 



* Read before the Philosophical Society of Glasgow, Ji'ebruary 5, 1845. 

 f See a paper on this subject by Dr. Buchanan, Proceedings of the Phi- 

 losophical Society of Glasgow, vol. i. p. 226. 

 X This test for sulphur in albumen was employed in 1812 by Vanquelin. 



