CHEMICAL CHANGES. 79 



possesses, and which it has inherited from pre-existing 

 particles. The nutrition of cells of epithelium of man is 

 conducted upon the same plan. See p. ST. At present we 

 cannot get further than this. I am ignorant of the nature 

 of the changes which occur, but I think the facts as I have 

 stated them are true. 



Is a Tissue living because attached to a Living Organism. 

 Some appear to think that a change in position only will 

 make all the difference as regards the proper application of 

 the term vital, and seem to hold that a tissue should be 

 called alive as long as it remains attached to a living body, 

 dfca^/when detached, irrespective of changes occurring in the 

 tissue itself. But it is obvious that a leaf, or an elementary 

 part, may be as devoid of life while it remains attached to 

 the living trunk as after its connection with it has been 

 completely severed. To say that a dead leaf exhibits life as 

 long as it hangs on to the branch would be absurd, because 

 differences of a much more important character proclaim 

 whether the leaf be alive or dead, irrespective of its con- 

 nection with the tree. 



Not long ago, it was stated that a living thing might 

 spring from a dying or dead one, as a fungus from a dead 

 elm, by mere transference of force from the latter to the 

 former, that the departing life-force of one thing became 

 transformed into the life of the new one, but those who 

 advocated this view failed to prove that the fungus did not 

 grow from the germ of a pre-existing fungus, and lived upon 

 the disintegrating elm as other living things consume other 

 kinds of pabulum. 



Chemical and Mechanical Changes in Living Beings. 



