110 INTRODUCTION TO SCIENCE 



(iii.) But within the general science of Biology 

 several quite different questions are asked, and 

 the answers to these are the sub-sciences. The 

 questions that the biologist must ask and answer 

 before he can go far in generalization appear 

 at first sight to be very numerous and varied, 

 but, from a certain distance, we see that there 

 are only four: What is this living creature as 

 regards form and structure? How does it work? 

 Whence has it arisen? How has it come to be 

 as it is? 



(1) What is this in form and structure, in 

 symmetry and internal architecture? It seems 

 a "simple question," but how hard to answer, as 

 we press it farther and farther home, as we pass 

 from external features to internal structure, 

 from organs to tissues, from tissues to cells, as 

 we put one lens after another in front of our own, 

 as we call to our aid all sorts of devices scalpel 

 and forceps, razor and microtome, fixative and 

 stain! "What is this," we say, "in itself and in 

 all its parts? what is this by itself and when com- 

 pared with its fellows and kindred? " and our 

 answer broadens and deepens till it furnishes the 

 raw materials of the sub-science of morphology. 



(2) Close upon the first question What is 

 this? there rises a second How does this work? 

 "It is equally natural and necessary, and through- 

 out the progressive periods in the history of Biol- 



