I thank you very much indeed for the compliment you are paying me in inviting me to give the James Scott Lecture. It is always an honour to be asked to give a lecture which is, as the nursery-man would say, a “named variety”, and in addition I welcome this invitation from a Society of which I am proud to be an Honorary Fellow.

Your lecturer is invited to talk about “fundamental concepts of Natural Philosophy” and I confess that this set me quite a task. It is one thing to talk about some special branch of research in which one is interested; it is quite another to review in a broad way some general feature of science. It asks for a philosophical approach, and I am not only a poor philosopher but also in a country where philosophy seems to flourish on the native soil. I hope therefore that you will receive what I have to say indulgently.

The fundamental problem in transplant surgery is that of preventing the immunological reaction which invariably occurs when an organ is transplanted between individuals, other than identical twins, and which brings about the destruction of the transplant. This reaction can be suppressed by a variety of agents but none of them is entirely satisfactory and there is a great need to find new ones which will be more effective and, in particular, more specific in their action. It was for this reason that anti-lymphocytic serum was first developed.

It is the custom of our Society that the President of the day should at some period in his term of office address the Fellows. The manner in which he interprets this charge will, of course, vary according to individual preference, but for obvious reasons, he usually elects to give his personal interpretation of that area of science in which he is himself most deeply concerned.

The Wellcome Foundation is part of the M.R.C. Working Party on A.L.S. and the main role of the Foundation, as agreed with the Working Party as a whole, is to produce A.L.S. on a large scale for use in man.

In Great Britain, the use of any new therapeutic agent is controlled by authority, in this case the Dunlop Committee. Before this committee could be approached for a licence to market such a product, it would be necessary for the pharmaceutical company concerned to have established conditions for large-scale production.