10 GENERAL HISTOLOGY. 



logical conditions, were never alive, although the product of 

 life. The only unexceptional characteristic of living bodies 

 consists in the presence of living matter, or bioplasm. This 

 is a structureless, jelly-like substance, either scattered in 

 minute particles or arranged in fibrils or networks through 

 nerves, muscles, bones, skin and every other tissue. 



2. All animals and vegetables, and all their varied tissues, 

 originated in such bioplasm. This jelly-like substance is found 

 in every living thing, and it is not found in any dead thing. 

 It may be properly called the histological unit, since every 

 tissue and organ of every living body is formed by it. 



3. To the eye or the microscope all bioplasm appears alike, 

 whether in man, horse or monkey, oak or fungus. There is 

 no way of distinguishing one kind from another but by ob- 

 serving what they do. One kind remains a single mass of 

 bioplasm during all its life history; others will divide and sub- 

 divide in various forms, so as to make all the complex organ- 

 isms of the living world. 



4. Bioplasts, or individual masses of bioplasm, used to be 

 called cells, and are still so called in some text-books. It was 

 supposed they were always covered by an integument called 

 the cell wall. In most bioplasts there is a sort of concentra- 

 tion of material called a nucleus, and in some nuclei there are 

 further condensations called nucleoli. Recent histology has 

 shown that many bioplasts have neither cell wall nor nucleus, 

 and that it is probable that most of the bioplasm in a living 

 body exists as a communicating network. In an embryonic 

 condition, however, it is a single particle, or microscopic mass, 

 which we may term a .cell, if we are not misled by the name 

 to regard it as a bladder-like vesicle, instead of an indefinitely 

 shaped particle. 



III. THE PHYSICAL FORCES IN BIOPLASM. 



I. Bioplasm exists in a colloid state; that is, like glue, 

 gum, etc. Professor Graham taught the distinction between 

 colloid and crystalloid material, especially in relation to the 

 physical processes called diffusion and osmose. These processes 

 are constantly active in living as well as in non-living matter. 



