136 LIFE IN NATURE. 



with a stern clutch she snatches from our fellows. 

 But we are honest debtors, and pay to the last 

 farthing. 



Besides the three points to which we have directed 

 our attention, there are very many other questions 

 which living bodies suggest, and which equally 

 deserve inquiry the causes, for example, of the dif- 

 ference between the animal and the vegetable, or 

 between the various textures of which our own bodies 

 consist ; by what physical necessity bone is formed 

 in one part, muscle in another, and nerve in a third : 

 why the circulating fluid of plants, as a rule, contains 

 green particles, and that of animals red ones, these 

 being complementary colours, which together con- 

 stitute white light : how the various changes which 

 take place in the gradual development of the organ- 

 ism, from childhood to adult life, are effected, and to 

 what deep principle of universal order they conform. 

 These and innumerable other subjects, which physio- 

 logy presents on every hand, claim, and doubtless 

 would well repay our pains. 



But looking only to the conclusions indicated 

 above, do they not advance us a step towards a 



