=:hungen mit dem Polarisationsmikmskop." Max Jan& '0 Verlagsbuchhandlung. Leipzig, 1934. (8) SCXMDT, "Die Bausteine des Tierkihpers in Palarisiertem Lichte," Friedrich Cohen, Bonn, 1924. (9) W~CHELL, "The micrmcop~ccharacters of artiiieiat in-
organic solid substances or artificial minerals," 2nd ed. John Wiley and Sons,Inc.. New York City, 1931. (10) Wnroar. "The methods of petrographic-mkmsropic m search." Carnegie Institution of Washington, Washing
THE DEMONSTRATION OF AN INDUCED, OR COUPLED, REACTION .
JAMES B. SUMNER Biochernistcr L&mtoy,
Gonull University, Zthaca, New York
DEMONSTRATIONS are sometimes diflicnlt to conduct successfully and are not invadably illnminating or instructive even when successful. The coupled oxidation of carotene, which occurs when a &ace of unsaturated fat, soap, or free fatty acid is pero%idized by lipoxidase,'. = an enzyme abundant in mybean meal, makes a demonstration which iB @afW&oty in many respects. Thisdemonstration illu&.rat@s: 1. 2. 3. 4. 5.
Enzyme action. The pre~enceof double bonds in afat. Peroxidation of a fat. An instance of an induoed reaction. The detmctionof -0tene by 0xidati~n.
The directions are as follows: Place 5 cc of acetone-alcohol solution of crystalline carotene in a dry 250-cc. Erlenmeyer flask and 5 cc. in a second flask. To the fist flask add a very small drop of cottonseed, hempseed, or raw linseed oil, or the respective soaps, or the free fatty acids. Mix, and then add to both flasks 100 cc. of water. Add 2 to 3 cc. of M / 2 phosphate b d e r of pH about 6.5.
AND
DOUNCE, Ensymolo ia 7, 130 (1939). J. M. 531 (w.
S-R,
cL.,
Now add 5 cc. of aqueous soybean meal extract and mix. The yellow wlor will disappear very rapidly from the flask to which the fat, soap, or fatty add w a added. The carotene in the second flask will undergc a slow spontaneous oxidation but some color will persist for as long as 24 hours. In this experiment lipoxidase transfers moleculat oxygen to the double bonds of the unsaturated fat, forming peroxides. In the act of forming the peroxides the carotene is somehow oxidized. Fatty acids which are already peroxidized have very little action upon carotene. PESPARATION OF REAGENTS
Carotcnc Solution.-Dissolve about 80 mg. of aye e e catotene (90 Per cent beta and 10 per cenf alpha) in 200 cc. of =tone and 400 cc. of alcohol. PhQsfihak 3@3'.-Mix 60 cc. of 2 / M N%HPO, 40 cc. of M / 2 -04. The solution will have a PH of about 6.5 when diluted. L~$o~ SoCs utic01z.-Mix 10 g. of defatted soybean meal with 100 cc. of water and centrifuge to clarify. The supernatant is employed. I t will keep for a week or more if preserved with a few drops of toluene and kept in the ice ch
THE COOPERATIVE COMMITTEE ON SCIENCE TEACHIN UNDER the spommship of five scientific societies representing biology, chemistryemistry mathematics, physics, and research in deace teaching a committee has been formed to work on educational problems of vital interest to all science teachers which no single organization can solve working alone. The committee is known as the mperative Committee on Sdence Teaching. Two meetings have been held, one in April and one in November, 1941. Work is now in progress on four problems: 1. Lieensing or certhkation of secondary-school science teachers. The committee hopes to work out a solution that will be practicable and that will he adopted by certifcation authorities. 2. The college training of prospective science teachers. It is desirable to prepare teachers for teaching certain combinations of subjects rather than to prepare intensively in one subject. 3. Exploratory studies of the secondary-schwl sdence mriculum. The Committee hopes to stimulate a number of colleges and universities to organize workshops and conferences for bringing together secondaryschool teachers to work on their edu-
.
Problems of state or local agencies needing the d c e s of
pducational ronsultants on questions pertaining to science teach ing. The Cnmmittee d e r s its services as a consultant to state or local agencies working on problems pertaining to science teach. ing. The Committee consists of the following members. Representing the American Association of Physics Teachers: K. Lark-Homvitz, Purdue University; Glen W. Warner, W b n J u n k College, Chicago. Representing the American Chemical Society: B. S. Hop*, University of Illinois; Martin V. McGiU. Lmain High Schwl, Lorsin. Ohw. Representing the ath he ma tical Association of America: A. A. Bennett, Brown University; Raleigh Schorling, Universiw of Michigan. Representing the National Assodstion for Research in Science T d n g : G. P. Cah-. Ohio State University; Robert J. Havighurst, University of Chicago. Riddle, Representing the Union of Biological Societies: 0Csrnegie Station for Experimental Evolutiou. Robert J. Havighurst is Chairman of the Committee and Glen W. Warner is Secretary.
