THEORIES AND PROBLEMS OF CANCER 



PART I 



By CHARLES WALKER, D.Sc. 



Whatever may have been the case in the past, as far as our 

 knowledge goes, at the present time, living matter exists only 

 in the form of small masses of a complex jelly-like substance 

 known as protoplasm ; these masses of protoplasm are called 

 cells. As a rule, the cells are so small as to be quite invisible 

 to the naked eye ; under the microscope, however, they are 

 seen to be composed of certain definite parts. 



Living organisms, including both plants and animals, for 

 convenience, may be divided into two great groups, the uni- 

 cellular — in which the individual contains but a single cell ; 

 and the multicellular — in which the body of the individual is 

 composed of a number of cells. Both unicellular and multi- 

 cellular organisms react to external stimuli. The unicellular 

 animal will seize particles of food, will swim away if disturbed 

 and may form for itself a covering if the particular puddle of 

 water in which it lives be dried up ; a plant will grow towards 

 the light ; a very definite response is given by a man if some 

 one tread upon his toe. 



It is obvious that in the case of unicellular organisms the 

 reactions take place entirely within the single cell and that 

 in order to produce an effect upon a number of separate cells 

 the stimulus must be applied to each individually. The way 

 in which multicellular organisms react to stimuli is very different. 

 All the cells composing the body of the animal or plant may 

 respond to a stimulus applied to only a few; on the other hand, 

 the stimulation of one group of cells may be followed by a 

 reaction in an entirely different group. A large proportion 

 of the body of a man responds to a sudden and violent pressure 

 upon the toe ; saliva drips from the mouth of the hungry dog 

 when he sees food. 



It is obvious, therefore, that in multicellular organisms there 



is some interaction between the cells and groups of cells which 



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