102 THE INFLUENCE OF INANIMATE SURROUNDINGS. 



three or four years, a winter overcoat, the necessity for a certain 

 annual expenditure of a sum of certainly not less than a hundred 

 thousand dollars would also be removed, and an enormous number 

 of the population would be thereby deprived of the means of 

 existence. Animals, however, under these circumstances behave 

 very differently ; the lower animals, and above all those that 

 live in the sea, are far less dependent on variations of tempera- 

 ture than man and the warm-blooded animals; nevertheless 

 the very simplest of all forms, the Protozoa, are dependent on 

 warmth in a very remarkable manner. 



Many of my readers have no doubt been at some time 

 obliged to experience some degree of acclimatisation to a tropical 

 climate. Everyone who has passed some time between the 

 tropics knows that sooner or later he got accustomed to the 

 higher temperature, and at the same time probably lost the good 

 appetite which he enjoyed in his colder native country. He 

 will also have observed that the effect of a high temperature 

 on the action of the sweat-glands and kidneys was different 

 from that of a colder climate. A European sees the natives 

 of a tropical country turn drowsy or shiver with cold at a 

 degree of temperature which, though low in those regions, would, 

 in his own countiy, have made him wish to fling off his gar- 

 ments and plunge into icy-cold water ; but a prolonged residence 

 in the hotter climate will gradually accustom him to the sensi- 

 tiveness of the natives to small variations in temperature. The 

 natives of Port Mahon in Minorca were excessively astonished 

 at seeing me and two other Germans bathe regularly in the 

 sea in the month of September, although the temperature of the 

 sea- water of the harbour where we bathed was certainly not less 

 than 18 centigrade, and very probably more. 



These few facts may suffice ; I should not have mentioned 

 them if it had not seemed desirable to make the reader familiar 

 at once with the idea that the influence of temperature on 

 animals depends not merely on the absolute degree of heat 

 experienced, but on the variations of temperature to which every 

 animal, almost without exception, is exposed in the course of its 

 life. The above-mentioned facts prove too that animals are 

 capable of enduring the effects of change of temperature and to 



