My dear Sir

I am ashamed to see the date on this & to compare it with that upon yours¹ most especially as my excuse for delay is insufficient when I come to look fairly at it although when hazily regarded in the way one sometimes looks at such things it seemed to me to assume larger proportions than it does now when I bring it into focus. I don’t know indeed how to present it, so insignificant does it look without the hazy medium which I can’t give but the whole is that finding one of my reagent bottles empty I wanted to replenish it from my stock at the Hospital² & regularly forgot to replenish while there till so many days had passed that I thought I must needs give you the whole answer to your other questions as well as that regarding the milk in my reply but unfortunately find I can’t do so till some day next week & so I write now as I am thoroughly ashamed of my delay.³ The part of the slide nearest the label & which seemed to you the best contained small refracting bodies which were either oil or resin. They were soluble in ether but so was the resin also with which the glass was secured   I suppose however that they presented much the same appearance before the balsam was put on & therefore think that one may say with confidence that they were oil. In the other part of the slide were several bacteria. They seemed to refract light more strongly than usual but D^r. Ferrier who worked at the subject of low organisms for several months felt almost certain that they were bacteria.⁴

It is very odd that adding a minute drop of hydrochloric acid of 1 per cent should stop the digestion of albumen while a drop of $\frac{1}{2}$ per cent should not. Too strong an acid certainly stops the digestive action of pepsin but the strength of 1 per cent (of ordinary acid = ·318 of real acid) is not very far from that which Brucke found to digest albumen most actively.⁵ For fibrin the best strength was 2·7 & 2·76 per cent of commercial acid when raised to 4· per cent digestion became much slower. When the acid was diluted digestion became gradually slower to 1·38 & 1·41 & when the dilution had reached ·69 digestion had become considerably slower. The best strength for neutralized white of egg was between 3·77 & 5. For not neutralized albumen 5·46. These numbers are taken from the abstract of Brücke’s paper in Canstatts Jahresbericht & I have converted the amount of absolute ClH in a litre which he gives into commercial acid per cent.⁶

Commercial pepsin consists of the cells lining the stomach scraped off with a blunt knife & dried & contains a good deal of albuminous material. I don’t think I have ever got it quite dissolved in any of my experiments but I have not yet ascertained even approximately what proportion remains undissolved I hope to be able in a few days to give you the results of the digestion of bones & of urea & shortly after some facts about digestion by the papaw⁷

I remain my dear Sir | Yours very truly | T Lauder Brunton