116 



SCIENCE. 



[N. S. Vol. I. No. 5. 



is the only layer of the retina which is af- 

 fected by red, yellow and green light is not 

 wholly conclusive. The interpretation of 

 the new facts and their bearing upon sev- 

 eral theories of light sensation were dis- 

 cussed. 



[This paper will appear in full in The 

 Psychological Review for March, 1895.] 

 The Influence of loiv Percentages of Alcohol 



upon the Gh'oivth of Yeast. C. F. Hodge. 



The influence of decomposition products 

 upon cellular metabolism is a question of 

 wide physiological interest and has in- 

 creased in significance since the advance- 

 ment of recent theories regarding autointox- 

 ication. Do the decomposition substances 

 of initial activity stimulate the cells to more 

 'active metabolism? Aside from the gen- 

 eral question of the physiological effect of 

 alcohol upon cellular processes, the influ- 

 ence of alcohol upon the ceU which produces 

 it would seem to be one of the best instances 

 upon which to test the theory of autointox- 

 ication. Yeast can grow in a saccharine 

 solution until by the decomposition of su- 

 gar it has brought the alcohol content of 

 the liquid np to 14%- With a greater 

 amount of alcohol no growth is possible. 

 Fliigge also states that at 12% growth is 

 hindered. Experiments were made with ex- 

 ceedingly attenuated piure cultures in large 

 amounts of nuti'ient solution, containing 

 from .01^/,, .1% up to 14 (fo. Counts were 

 made as often as possible during the first 

 three days. The general result up to the 

 present is that yeast grows nearly twice as 

 fast in pure solution as in 1% alcohol. 

 An average of nine experiments thus far 

 give the following figures representing pro- 

 portional growth in the various cultures. 

 Growth in: 0%, 1%, 2%, 3%, 4%, 5%, alcohol. 

 77, 45, 16, 1.5, 0.3, 0.11. 



Beyond 5% no growth appreciable by the 

 method employed occurred within the three 

 days. In cultures containing 0.1% and 

 0.01% growth was considerably less than 



in the normal solution ; but it is desirable to 

 experiment further before gi^ang the figures. 

 As yet no evidence in favor of autointoxi- 

 cation theories has been obtained. 

 A Means of Recording Daily Activity of Ani- 

 mals and the Influence upon it of Food and 

 Alcohol. C. C. Stewart. (Introduced 

 by C. F. Hodge.) 



Tlius far the animals experimented on 

 have been rats, mice and squirrels. They 

 are kept in circiilar, easily rotated cages, so 

 arranged that anj' motion of the animal 

 rotates the cage, and by means of a tambour 

 or levers this motion of the cage is recorded 

 upon kjonograph paper kept mo\ing night 

 and day. An electromagnetic circuit with 

 a clock marks hours and minutes. AVe thus 

 have the manner in which an animal di- 

 vides his time between rest and activity 

 recorded by himself. Eats and mice divide 

 their days into about 12 hours rest and 12 

 hours intermittent work during the night. 

 During the work period, short intervals of 

 activitj', rarely exceeding an hour, are in- 

 terrupted by almost equal periods of rest. 

 The squirrel, in winter, works almost con- 

 tinuouslj' for from twenty minutes to two 

 hours early in the morning, with sometimes 

 a short interval of activity late in the even- 

 ing, and rests nearly 22 hours in the day. 



Food has a most marked influence upon 

 diurnal activity. In general the richer the 

 diet in proteid, the greater the activitj'. Fat 

 has the opposite effect, reducing the activity 

 of mice from 6 to 8 hours' actual work to a 

 few minutes a day. To test the influence 

 of alcohol on spontaneous activity, rats 

 kept on drjr corn were given instead of 

 water alcohol of from 5% to 60%. During 

 50 daj'S of his treatment, no uniform effect 

 of the alcohol could be demonstrated. All 

 normal animals experimented on tended to 

 woi"k more minutes per day, when barome- 

 tric pressure was high, and this miist be 

 taken into careful account in estimating the 

 effect of any condition upon daily activitj'. 



