2 LIFE: OUTLINES OF GENERAL BIOLOIA' 



ticular — yet many-sided and even protean — activity in colloidal 

 protoplasm; but it is more profitable to lay the first emphasis on the 

 everyday activities of the organism as a whole. Hence the second 

 part of this Introduction deals in a broad way with the charac- 

 teristics of living creatures — Lives in being. 



ECOLOGICAL. — Here our initial question changes its form; and 

 we are led to inquire into the ways of living creatures as they 

 live in Nature. In the mood of the old-fashioned Natural History, 

 but with the precision which renews this as Ecology, we here study 

 organisms in relation to their environments, and in the seasonal 

 and other changes of these. This discloses a web of inter-relations, 

 a vibrant Systema Naturae — say, rather, Drama Naturae — in which 

 nothing lives or dies to itself. For there is a fascinating variety in 

 the nutritive chains which bind living creatures together in a series 

 of successive re-incarnations or re-embodiments; there are helpful 

 partnerships like commensalism and symbiosis, yet there is also 

 predatory life, and the competition it so especially provokes; yet 

 also there are evasions of the competitive struggle for existence, as 

 in the sheltered nooks of life, or in parasitism. Thus the part of this 

 book that is headed ecological is naturally long as well as varied. 

 This mode of approach is, we submit, psychologically natural, and 

 it corresponds with the historical development of biological science. 



PHYSIOLOGICAL.— But equally essential and irrepressible is the 

 physiological question: How does this organism work? How does 

 it keep going? How does it feel and move? How does it grow 

 and multiply? How does it waste, yet recover itself? And finally, in 

 all but the simplest, how does it die? Here we brush aside the old 

 answers which speak of "vital spirits" and "vital force", of "prin- 

 ciples of life", and so on, yet not forgetting that we may sometime 

 rehabilitate the truth in such too abstract expressions. More reso- 

 lutely than in old days, we have to analyse the workings of the 

 different organs which co-operate in the life of the whole, such as 

 the throbbing heart and the churning digestive stomach; we pass 

 beneath this to study the tissues that build up the organs: the 

 contracting muscles, the thrilling nerves, the secreting glands; 

 we inquire yet more penetratingly into the waxing and waning of 

 the component cells; and at length we reach the complex chemical 

 and physical changes that go on in the protoplasm. And as the 

 intricacy of these internal activities impresses the student, the 

 question naturally arises how they are all integrated — as it were 

 orchestrated — so that the result is efficiency of action and the 

 harmonious vigour of positive health. The answer to this question 

 leads beyond the integrative functions of nervous and circulatory 

 systems to the modern discovery of the regulative r61e of "hor- 



