6 AN ELEMENTARY PART. 



in water, and living things on or in the ground, may 

 in like manner be divided into (1) those which con- 

 sist of living matter capable of moving in every direc- 

 tion, of dividing and subdividing, and invested only 

 with a very thin layer of fluid or semifluid matter, 

 and (2) those which are covered with a layer of a 

 more or less resisting material, which interferes with 

 or entirely prevents such movements of the living 

 matter as have been referred to above. 



10. An elementary part. So also the elementary 

 parts of which all the tissues and organs of man and 

 all the higher animals are composed are found to con- 

 sist of these two classes of particles the first exhibit- 

 ing the general characters already described, the last 

 manifesting a great variety of form, structure, and 

 properties, according to the arrangement, character, 

 and composition of the external or enveloping matter. 



The great difference between particles of apparently 

 naked matter and particles enclosed in a thick en- 

 Telope or capsule is but a difference of degree. The 

 first, or apparently naked particles, are perhaps in- 

 Tested with so very thin a layer of soft and perhaps 

 fluid formed substance that it follows the movements 

 of the living matter, and is almost invisible ; while 

 in the last this formed matter has increased in thick- 

 ness, and has undergone condensation, so as to inter- 

 fere with the free motion of the living matter within, 

 or, at most, to permit it only to move round and 

 round within its prison wall. Our investigation is 

 therefore narrowed to the study of the changes taking 

 place in the transparent living matter itself, and the 

 production of the material upon its surface. 



11. First stage of being of every living- thing. - 

 Even man and the higher animals, as well as every 

 other living thing, begins its life as a minute spherical 

 particle, hardly to be distinguished from those minute 

 particles of simple living matter suspended in the 

 air ( 6). The particle consists of colourless trans- 



