324 SCIENCE PROGRESS 



The former react to changes in the temperature of their surroundings by 

 altering their heat production and heat loss so as to attempt to maintain 

 a temperature within a narrow range. The latter tend to a temperature 

 approximately that of their surroundings. When the temperature of the 

 surroundings is altered, there is a period of warming or cooling which must 

 be neglected if one is studying the effect of steady temperatures. Further, 

 if the animals are kept at a high temperature for some time, there is a falling 

 oflE in their activity. 



The rates of movement of two species of worms and of a snail were studied. 

 The results were treated from the physico-chemical point of view. 



With rising temperature there is an increase in activity up to an optimum 

 above which the activity rapidly decreases. The author's results, as well 

 as those of previous observers, are discussed. The rate of movement probably 

 depends on the rate of a chemical reaction. Therefore it depends on the 

 concentration of reacting substances, on the change of rate with change in 

 temperature, and on any physical modifications of the system caused by the 

 temperature. The first of these is independent of the temperature, but may 

 be afiected by the duration of the experiment. The second is expressed by 

 the Law of Van't HofE and Arrhenius, whilst the last has been studied by 

 examining the tissue fluids by means of the ultramicroscope. 



The results show that the optimum is due to the crossing of the curves 

 of increase in activity with rise of temperature and that of the physico- 

 chemical changes in the colloids at high temperatures. The longer an animal 

 is kept at a high temperature, the greater is the latter effect. The three 

 variables — rate, temperature, and time — are expressed geometrically by a 

 surface from which one can read either the variation of rate at the same tem- 

 perature (isothermal lines) or after equal durations (isochronic lines). 



The motor reactions show evidence of four rhythms : (i) A gradual 

 decrease during several days due to a cumulative effect of the temperature ; 

 (2) a daily rhythm due to inactivity during darkness, with an accumulation 

 of reserves of material for activity ; (3) an hourly or multi-hourly rhythm ; 

 (4) a rhythm of short duration probably of the nature of an autocatalytic 

 reaction. 



The action of drugs is modified by the temperature. At high temperatures 

 the reaction may be so violent as to kill the animal, but at a low temperature 

 the same dose may be harmless because the reaction is less violent, so that the 

 drug may be excreted without fatal effects. 



This book is intended as a first approximation to the intimate mathe- 

 matical analysis of the effect of temperature on living organisms, and it should 

 be read by all interested in the subject. 



H. E. R. 



Altitude and Health. By F. F. Roget. [Pp. xii -f 186.] (London : Con- 

 stable & Co., 1919. Price 125.) 



This book is concerned with the effect of altitude in relation to the main- 

 tenance of health and to the cure of respiratory diseases such as pulmonary 

 tuberculosis. It is divided into three parts : namely, I, Climate (Alpine 

 and Northern) ; II, The Air at Altitudes ; III, Sunlight and Sunheat. These 

 three represent three physical conditions associated with high altitudes, 

 which are a fall in temperature, a decrease in atmospheric pressure, and an 

 increase in the radiant energy of the sun. 



Low temperatures can be reached by going to high latitudes, but this fall 

 in temperature is not associated with a decrease in atmospheric pressure. 

 In addition, at high latitudes the radiant energy of the sun is less because 

 the rays pass through a thicker layer of atmosphere, wJiich absorbs heat and 

 ultraviolet rays. 



