192 HUMAN BIOLOGY 



Like criminals (see Chapter xv) they become antisocial. They 

 grow unrestrictedly, invade the territory belonging to the 

 other cells, pilfer their food, which they can ill afford to 

 lose, and so completely disrupt established conditions that 

 community life is no longer possible. But, again like crim- 

 inals, the cells do not embark upon this mad career merely 

 out of perversity. Beforehand they are injured in some 

 way which we do not at all understand. They are the victims 

 of some intangible kind of misfortune. They have been 

 designated "anarchists" by tumor specialists. As a result 

 of their activity one in every seven of us dies of cancer 

 (see Chap, xviii). 



It is a curious fact that although death in one way or 

 another is thus inevitable for the individual, there is reason 

 to suppose that it is apparently not so for special groups of 

 cells removed from the body. Carrel has found that when 

 cells known as fibroblasts are taken from the body and 

 cultivated in appropriate media, which are changed at 

 stated intervals, they will live as far as we can tell at present 

 forever. 



MICROSCOPIC STRUCTURE OF CELLS 



The properties of living cells are so challenging that it is 

 not surprising that many attempts have been made to 

 ascertain the structural basis of life. The problem is obvi- 

 ously a difficult one. Thus far a beginning has hardly been 

 made, although it has been possible to recognize certain 

 elements within the cell. 



A gland cell of the stomach, for example, when magnified 

 about 4000 times, is represented in Figure 2. It possesses a 

 very flexible and delicate cell membrane by which is enclosed 

 a mass of watery material. In it may always be seen a large 

 oval or spherical structure, the nucleus, which we mentioned 

 at the beginning of the chapter. It was discovered by the 

 Englishman, Robert Brown, in 1831. The fluid contents of 

 the cell, other than the nucleus, are known as the cytoplasm. 

 In addition, one may observe various granules in this case 

 consisting of mucus, or slime, which is about to be poured 

 into the cavity of the stomach. 



