Dear Mr. Darwin,

I have examined the specimens you have kindly sent me, and I find that although the specimen marked as “fibro-cartilage from artificial gastric juice” is undoubtedly very different from the specimens contained in the unlabelled leaves, still I have little doubt that the leaves have acted upon the fibro-cartilage.¹ The specimen marked as “f.c. from art. g. j.”² ⁠⟨⁠5 lines excised⁠⟩⁠

In those specimens, that were contained in the unlabelled leaves, although only slightly altered, still there were distinct places, which have become altered in A similar manner, viz. more transparent, almost hyaline and the fibrillation of its bundles indistinct. I fancy the specimen contained in the leaf marked by a white thread (that on which some saliva had been placed) was most changed, next comes one that was smaller than the other two of the unlabelled leaves.

I will not omit to repeat, dear Sir, that it gives me the greatest pleasure if I can be of any service to you.

Believe me very sincerely | yours | E. Klein.