X A FOREWORD TO THE STUDENT 



tolerate by way of handling, and what destroys 

 them, that we gradually acquire a "feel" for 

 proteins and nucleic acids, just as one does for 

 organisms. Indeed, the one greatly helps the 

 other, for many of the basic properties of living 

 organisms derive from their proteins and nucleic 

 acids. Here again it is only long experience 

 with these molecules in their great variety that 

 develops the intuitions that give point and mean- 

 ing to our concepts. 



This is our aim in the laboratory, therefore — 

 to make direct contacts with living organisms 

 and with the molecules that compose them. A 

 great Harvard biologist, Louis Agassiz, the 

 founder of the Museum of Comparative Zool- 

 ogy, is often quoted as having said, "Study 

 nature, not books." The statement is a little 

 foolish if taken literally; for one thing, you 

 have just read it in a book. I think he really 

 meant that we should do both but wished to 

 remind us that studying nature is a very different 

 thing from studying books, and at times more 

 reliable. In any case, our job in the laboratory 

 is the study of nature itself. 



We will pursue it there for its own sake, not 

 merely to illustrate and amplify the content of 

 the lectures. Indeed, laboratory work develops 

 on its own, independently of the lectures; and 

 you should approach it with this in mind. If 

 something comes up in the laboratory that has 

 not been mentioned at the lectures, as will hap- 

 pen regularly, master it then and there. We will 

 try to help you in every way we can, but much 

 of it is up to you. Know what you are doing in 

 the laboratory at all times. No mistake would 

 be as great as to go through a laboratory session 

 in a state of confusion, hoping that some later 

 lecture will clear it up. We hope that later 

 lectures will make things clearer. In fact, we 

 hope the whole course hangs together in that 

 regard. But each laboratory experience must be 

 met on its own terms, then and there. 



One last word : your business in the laboratory 

 is with living organisms and the molecules that 

 compose them. This laboratory guide, your 

 instructors, the instructors' questions, are all to 

 help deepen and enrich that experience. They 



are not objectives in themselves. Come to the 

 laboratory as a scientist, to put questions direct 

 to nature. Experiment and observe generously, 

 not just what we suggest, but whatever interests 

 you. Try to raise your own questions; we will 

 appreciate them more than the ones we ask you. 

 This is your opportunity to have a meaningful 

 experience with a lot of things you may never 

 have in your hands again. Make the most of it. 



A few technical matters 



Notebooks. Get a three-ring loose-leaf note- 

 book for the laboratory and a block of unlined 

 paper on which you can take notes. Note down 

 whatever is essential in your experiments, in 

 good English and in good order, so as to give 

 a clear and connected account of what you have 

 done, your observations, and the results of your 

 experiments. Whenever a drawing helps, make 

 one. The point is for it to be clear and informa- 

 tive, not necessarily beautiful. 



Don't copy out sections of this laboratory 

 guide into your notes. Whatever you need to 

 describe, put into your own words. Answer all 

 questions. 



The notes may be in pencil or in ink. Draw- 

 ings, of course, are better done in pencil. Do 

 not use a soft pencil for either notes or drawings, 

 since it smudges. A No. 3 pencil is of about the 

 right hardness. 



Preparatory reading. At the beginning of each 

 exercise you will find references to textbooks and 

 often also to Scientific American articles. These 

 should be read before you come to the labora- 

 tory. Often it would be useful for you to have 

 a textbook in the laboratory with you, but only 

 for reference, not for extensive reading. Read 

 the directions beforehand on the experiment you 

 are about to undertake, and try to get a good 

 idea of what you will be doing and in what 

 sequence. The better prepared you are on com- 

 ing to the laboratory, the more you will get out 

 of it. 



The three books most commonly referred to 

 in the preparatory reading are: 



