20 BIOTIC STRUCTURE AND BIOTIC ENERGY 



man is laid down in the germinal cells, reminds one of Loewenhoek's 

 quaint notion that he saw the heads and faces of the future men and 

 women in the " homunculi " which his microscope demonstrated 

 to him for the first time. 



Given a definite, labile, colloidal structure specific for each 

 species of organism, and an initial energy charge upon this, then as 

 each stage develops it must automatically swing on into the next. 



The only experimental method whereby to penetrate as far as 

 possible into the mysteries of these cell changes which presents itself 

 to us at present is that of studying the effects of varying the 

 external stimuli and environmental conditions and nutrition, and 

 interfering artificially by physical and chemical means with the 

 cell processes. 



Such general study of cell growth under artificially varied con- 

 ditions will not only prove fertile in increasing our knowledge of 

 cell division, but will yield rich fruit in application to the study of 

 pathological processes and disease, notably in the study and elu- 

 cidation of cancer and other malignant growths. 



A tumour or growth, whatever may ultimately be found to be 

 its exciting cause or causes, is essentially a number of cells escaped 

 from the ordinary laws of growth of the organism, and it is benign or 

 malignant according to whether it lives apart by itself and inter- 

 feres with nothing else, or whether it invades and suppresses normal 

 tissues, gets carried to other regions, and starts secondary growths or 

 metastases, or gives out toxins and chemical products which inter- 

 fere with the general physiological well-being of the entire organism. 



The stimulus to the growth of abnormal tissue may be an irri- 

 tating micro-organism, as in the tubercles of tuberculosis and the 

 gummata of syphilis, or interference with nutrition by diminished 

 or increased blood-supply, as in scar tissue and nsevi, or stimula- 

 tion by foreign or pathological chemical substances, as in the tophi 

 of gout and nodules of cirrhosis, and possibly in cancer by altered 

 composition of blood-plasma, though here we know at present 

 nothing definite, and a micro-organism, bacterial or protozoan, 

 is by no means yet excluded. 



In many different ways energy may be thrown in from without, 

 and the normal processes of cell division, development, and growth 

 interfered with, and it is by experimental methods of this sort 

 that many of the most pressing problems of biology and medical 

 science will ultimately be solved. 



