THE BIOLOGY OF DAILY LIFE. 67 



has not originated, the notion that protoplasm is the 



"Physical Basis of Life." 



We cannot do better than quote his own words, no 



one has at his command clearer, more picturesque, 



and when the occasion calls for it, grander language. 



" You are doubtless aware that the common 

 nettle owes its stinging property to the 

 innumerable stiff and needle-like, though 

 exquisitely delicate, hairs which cover its 

 surface. Each stinging-needle tapers from a 

 broad base to a slender summit, which, though 

 rounded at the end, is of such microscopic 

 fineness that it readily penetrates, and breaks 

 off in, the skin. The whole hair consists of a 

 very delicate outer case of wood, closely 

 applied to the inner surface of which is a layer 

 of semi-fluid matter full of innumerable 

 granules of extreme minuteness. This semi- 

 fluid lining is protoplasm, which thus con- 

 stitutes a kind of bag full of a limpid liquid, 

 and roughly corresponding in form with the 

 interior of the hair which it fills. When 

 viewed with a sufficiently high magnifying 

 power, the protoplasmic layer of the nettle- 

 hair is seen to be in a condition of unceasing 

 activity. Local contractions of the whole 

 thickness of its substance pass slowly and 

 gradually from point to point, and give rise to 

 the appearance of progressive waves, just as the 

 bending of successive stalks of corn by a breeze 

 produces the apparent billows of a cornfield. 



" But, in addition to these movements and 

 independently of them, the granules are driven, 



