From T. L. Brunton   4 September 1874

My dear Sir

I am sorry that I have been so long in returning an answer to your questions but I asked a friend who was working at urea to make the determinations for me.¹ The first method I employed viz to mix urea with glycerine extract of pepsin did not answer as the glycerine disturbed the reaction so much. My friend was therefore obliged after several attempts, to desist—& he shortly afterwards left this country for a holiday excursion   Mr. Wharry a student at S^t. Bartholomews has been working at the determination of urea since the departure of M^r. West,² and he has kindly sent me the following analyses which show that the pepsin & hydrochloric acid alone disturb the analyses although glycerine be absent. They make it extremely probable however that urea is not destroyed by digestion. A mixture of equal parts of a solution of urea & of hydrochloric acid of .2 per cent was made pepsin added & the whole well shaken up   It was then divided into equal parts— One half was analyzed for urea at once— It gave 1.7 grammes per 100 cc. nearly the true content. The remainder was warmed to 40^oC & left for 48 hours. When analyzed it gave 2.8 grammes per 100 cc. The apparent increase is due to the evaporation of water against which sufficient precautions had not been taken. If any noticeable diminution in the quantity of urea had taken place I do not think this large increase would have occurred.³

I am sorry to say that D^r. Littlejohn’s supply of papaw was all gone when I applied to him some months ago.⁴ Whenever he gets a new supply he will send me some & I will let you know the result.

I have at last succeeded after