368 SISTER MARGARET ANN 



bodies." The most recent and perhaps the most comprehensive 

 review of this work was published by Dr. Brown in a recent 

 issue of Science. ^ 



Living organisms, Dr. Brown points out, inhabit a world of 

 rhythms.^ The whole physical world, from that of the orbiting 

 electrons in the atom to that of our planetary system revolving 

 about the sun, shows regular cycles, or periodic changes. There 

 are solar, lunar, tidal, monthly and annual cycles, which greatly 

 affect the animal and plants; but in spite of the ever-changing 

 environment, the organisms maintain a very constant homeo- 

 stasis.^ To maintain this marvelous constancy, the organisms 

 themselves have " built-in " rhythms that respond to the 

 periodic changes in their physical surroundings. There exists 

 an abundant literature describing observed rhythmicities of 

 various sorts of animals. These rhythmicities appear to be 

 inherent, for they persist not only when the animals are in 

 their own habitats, but even when they are removed from the 

 place where the particular periodicity seemed to constitute an 

 advantage for individual survival and that of the species.* 



Perhaps one of the most arresting examples of rhythms is 



^ Frank A. Brown, Jr., " Living Clocks," Science, CXX (1959) , 1535-1544. 



^ Frank A. Brown, Jr., " The Rhythmic Nature of Animals and Plants," Cycles, 

 XI (1960) , 81-92. 



^ Walter B. Cannon, The Wisdom of the Body (New York: W. W. Norton, 1932) , 

 pp. 20-21; Frank A. Brown, Jr., " The Rhythmic Nature of Life," in Recent 

 Advances in Invertebrate Physiology: A Symposium (Eugene, Oregon: University 

 of Oregon, 1957) , edited by Bradely T. Scheer. 



* Frank A. Brown, Jr., J. Shriner and C. L. Ralph, " Solar and Lunar Rhythmicity 

 in the Rat in ' Constant Conditions ' and the Mechanisms of Physiological Time 

 Measurement," Am. Jour. Physiol., CLXXXIV (1956) , 491-496; Frank A. Brown, 

 Jr., M. F. Bennett and H. M. Webb, " Monthly Cycles in an Organism in Constant 

 Conditions during 1956 and 1957," Proc. Nat. Acad. Sci., XLIV (1958), 290-296; 

 Frank A. Brown, Jr., R. A. Freeland and C. L. Ralph, " Persistent Rhythms in O2 

 Consumption in Potatoes, Carrots and the Seaweed, Fucus," Plant Physiol., XXX 

 (1955), 280-296; Frank A. Brown, Jr., M. F. Bennett, H. M. Webb and C. L. Ralph, 

 " Persistent Daily, Monthly and 27-day Cycles of Activity in the Oyster and 

 Quahog," Jour. Exp. Zool., CXXXI (1956) , 235-262; Muriel I. Sandeen, Grover C. 

 Stephens and Frank A. Brown, Jr., " Persistent Daily and Tidal Rhythms of Oxygen 

 Consumption in Two Species of Marine Snails," Physiol. Zool., XXVII (1954), 350- 

 356. 



