PROCESSES OF LIFE REVEALED BY THE MICROSCOPE. 389 



to sensation ; but what of living matter in the humbler forms where no 

 nervous system can be found? That these have vital motion, that they 

 breathe, nourish themselves, grow, and produce offspring, none can deny. 

 Do they have anything comparable with sensation? As most of the 

 lowest forms are minute, the microscope comes to our aid again, and in 

 watching these lowliest living beings it is found that they discriminate 

 and choose, going freely into some portions of theii liquid world and 

 withdrawing from other portions. If some drug which is unusual or we 

 must believe disagreeable is added to a part of the water, they withdraw 

 from that part. It seems to have the same effect as disagreeable odors 

 on men and animals. On the other hand, there are substances which 

 attract, and into the water containing these they enter with eagerness. 

 Strange is it, too, that, as proved by experiment, if an unattractive sub- 

 stance is used and also one on the other side that has been found still 

 more unattractive, the less disagreeable is selected ; the less of the two 

 evils is chosen. 



As man, the horse, dog, and many other animals adapt themselves 

 gradually to temperatures either very cold or very warm, and that, too, 

 by a change in their heat-regulating power rather than by a change of 

 hairy or other clothing, so these lowly organisms are found in nature 

 in water at temperatures from near freezing up to G0° or 80° C, a point 

 approaching that of boiling water. It may be answered that each was 

 created for its place, but by means of a microscope and a delicate 

 thermostat, to be certain of every step and to see all the results, Dr. 

 Dallinger, through a period of seven years, accustomed the same uni- 

 cellular organism and its progeny to variations of temperature from 

 15° to 20° 0., i. e., about the temperature of a comfortable sitting room, 

 up to 70° 0. For those at the cooler temperature it was death to 

 increase rapidly the heat 10°, and for those at the higher temperature 

 it was equally fatal to lower it to the original temperature of 15° to 20°. 

 These examples seem to show that it is one of the fundamental charac- 

 teristics of living substance, whether in complex or simple forms, to 

 adapt itself to its environment. 



There is another fact in nature that the microscope has revealed and 

 that fills the contemplative mind with wonder and an aspiration to see 

 a little farther into the living substance, and so perchance discover the 

 hidden springs of action. This fact may be called cellular altruism. In 

 human society the philanthropist and soldier are ready at any time to 

 sacrifice themselves for the race or the nation. With the animals the 

 guards of the flock or herd are equally ready to die in its defense. 



So within each of the higher organisms the microscope has shown a 

 guarding host, the leucocytes or white-blood corpuscles. The brilliant 

 discoveries in the processes of life with higher forms have shown that 

 not only is there a struggle for existence with dead nature and against 

 forms as large or larger than themselves, but each orgauism is liable to 

 be undermined by living forms, animal and vegetable, infinitely smaller 



