118 INTRODUCTION TO SCIENCE 



two sister sciences go hand in hand, for just as 

 taking a watch to pieces is not very intelligent 

 unless we inquire into the working of the various 

 parts, and just as we cannot understand how the 

 watch "goes" unless we know its structure inti- 

 mately, so anatomy and physiology must always 

 be closely linked together. 



There has been a close parallelism in the history 

 of the two sciences. The morphologist began 

 with the form of the intact organism, and passed 

 in succession to the various organs, their com- 

 ponent tissue, their component cells, and, finally, 

 to the structure of living matter itself. So 

 the physiologist investigates life or activity at 

 different levels, passing from his study of the 

 living creature as a unity with certain habits, 

 to consider it as an engine of organs, as an 

 intricate web of tissues, as a veritable com- 

 munity of cells, and, finally, as a whirlpool of 

 living matter. 



(3) The third question Whence is this? is 

 really double, for we may inquire into the devel- 

 opment of the individual (Embryology) or into 

 the history of the race as it is hidden in the 

 strange graveyards of the buried past, the fossil- 

 bearing rocks (Palaeontology). Since these are 

 both historical or genetic inquiries, the one deal- 

 ing with individual development (ontogeny), the 

 other with racial evolution (phylogeny), it would 



