Absence from home and consequent idleness are the causes that I have not sooner thanked you for your very kind present of your Lectures. (161/1. "On the Germs and Vestiges of Disease," (London) 1861.) Your reasoning seems quite satisfactory (though the subject is rather beyond my limit of thought and knowledge) on the V.M.F. not being "a given quantity." (161/2. "It has been too common to consider the force exhibited in the operations of life (the V.M.F.) as a given quantity, to which no accessions can be made, but which is apportioned to each living being in quantity sufficient for its necessities, according to some hidden law" (op. cit., page 41.) And I can see that the conditions of life must play a most important part in allowing this quantity to increase, as in the budding of a tree, etc. How far these conditions act on "the forms of organic life" (page 46) I do not see clearly. In fact, no part of my subject has so completely puzzled me as to determine what effect to attribute to (what I vaguely call) the direct action of the conditions of life. I shall before long come to this subject, and must endeavour to come to some conclusion when I have got the mass of collected facts in some sort of order in my mind. My present impression is that I have underrated this action in the "Origin." I have no doubt when I go through your volume I shall find other points of interest and value to me. I have already stumbled on one case (about which I want to consult Mr. Paget)--namely, on the re-growth of supernumerary digits. (161/3. See Letters 178, 270.) You refer to "White on Regeneration, etc., 1785." I have been to the libraries of the Royal and the Linnean Societies, and to the British Museum, where the librarians got out your volume and made a special hunt, and could discover no trace of such a book. Will you grant me the favour of giving me any clue, where I could see the book? Have you it? if so, and the case is given briefly, would you have the great kindness to copy it? I much want to know all particulars. One case has been given me, but with hardly minute enough details, of a supernumerary little finger which has already been twice cut off, and now the operation will soon have to be done for the third time. I am extremely much obliged for the genealogical table; the fact of the two cousins not, as far as yet appears, transmitting the peculiarity is extraordinary, and must be given by me. LETTER 162. TO C. LYELL. [February 17th, 1863.]