126 LAY SERMONS, ADDRESSES, AND REVIEWS. [vn 



functions, and one and the same portion of proto- 

 plasm may successively take on the function of feeding, 

 moving, or reproducing apparatus. In the highest, on 

 the contrary, a great number of parts combine to per- 

 form each function, each part doing its allotted share of 

 the work with great accuracy and efficiency, but being 

 useless for any other purpose. 



On the other hand, notwithstanding all the funda- 

 mental resemblances which exist between the powers of 

 the protoplasm in plants and in animals, they present 

 a striking difference (to which I shall advert more at 

 length presently), in the fact that plants can manufacture 

 fresh protoplasm out of mineral compounds, whereas 

 animals are obliged to procure it ready made, and hence, 

 in the long run, depend upon plants. Upon what con- 

 dition this difference in the powers of the two great 

 divisions of the world of life depends, nothing is at 

 present known. 



With such qualification as arises out of the last- 

 mentioned fact, it may be truly said that the acts of all 

 living things are fundamentally one. Is any such unity 

 predicable of their forms ? Let us seek in easily verified 

 facts for a reply to this question. If a drop of blood be, 

 drawn by pricking one's finger, and viewed with proper 

 precautions and under a sufficiently high microscopic 

 power, there will be seen, among the innumerable mul- 

 titude of little, circular, discoidal bodies, or corpuscles, 

 which float in it and give it its colour, a comparatively 

 small number of colourless corpuscles, of somewhat larger 

 size and very irregular shape. If the drop of blood be 

 kept at the temperature of the body, these colourless 

 corpuscles will be seen to exhibit a marvellous activity, 

 changing their forms with great rapidity, drawing iu 

 and thrusting out prolongations of their substance, and 

 creeping about as if they were independent organisms. 



