THE VICTORIAN NATURALIST. 155 



characteristics common to all protoplasm : it agrees with them in 

 life history, in chemical composition, and in growth and nutrition. 

 It runs through a similar series of changes, and passes on the 

 gift of life to a similar portion of itself. 



I. have said that the continual waste was being as continually 

 made good by a process of renewal and repair ; but the two do 

 not completely balance. Had they done so the individual might 

 have enjoyed a perpetual youth, but it is difficult to see how the 

 course of the great stream of life could have been ever onward. 

 After a time waste predominates over repair, and the individual 

 slowly withers, until at last waste has so far obtained the upper 

 hand that life is no longer possible so far as the protoplasm is 

 concerned. And then the individual dies. In the natural 

 sequence of events, the limit of the life of the various tissues of 

 which the body is composed varies greatly. These tissues have 

 all been derived from the one common protoplasm, but they 

 resist the wear and tear of life in varying degrees. Some parts 

 die and disappear in childhood, others in adult life ; and as old 

 age creeps on the failure in the vigour of the tissues is apparent 

 almost everywhere. The teeth decay and fall out ; cartilages and 

 sinews become bony from the deposition in them of earthy salts ; 

 the blood vessels suffer a like change, and even the seeing eye 

 grows dim, and the understanding brain fails to perceive. It is 

 conceivable that this gradual decay would have gone on till at last 

 death took place by imperceptible degrees, but the living frame is 

 such a complicated machine that death is always more or less 

 sudden and violent. One part breaks down and throws all the 

 rest out of gear. Life ceases not because every molecule and cell 

 is worn out, but because one part has given way, the activity of 

 which was essential to the preservation of the life of the whole. 

 Before leaving this part of the subject — where the end meets the 

 beginnings of life — let us notice how change is the very- first and 

 most fundamental law of all living matter. Astronomers tell us 

 that change is also the law of the whole universe ; that the planets 

 and the sun are growing cold ; that the stars, apparently fixed and 

 changeless for ever, are slowly changing too. Geologists tell us 

 that, as far as the surface of the earth is concerned, a few million 

 years will completely alter the face of the dry land. And as to the 

 ocean, what shall we say of it? "Time writes no wrinkles on 

 thine azure brow " may be poetry, but it is certainly not science. 

 Yet all these things are fixed and unchangeable compared to life : 

 with it to stand is to die, it must change or it ceases to be. And 

 what is more, life is no passive condition. Living protoplasm is 

 matter, so to speak, in a state of unstable equilibrium ; its ten- 

 dency is always to fall ; but it has within itself forces which are 

 able for a time successfully to defy its adversaries. It maintains 

 its fortress, though so far as we know this is but a solitary point in 



