DISCOVERY 



71 



riie Biological Problem of 

 Cancer 



By J. A. Murray, M.D. 



The Imperial Cancer Research Fund, London 



HE problem of the nature and causation of Cancer 



one of perennial and baffling interest. The disease 

 IS existed from the earliest times, and to-day still 

 ikes a heavy toll of humanity. Its ravages are not 

 mfined to mankind ; domesticated and wild animals, 

 rds and fishes, all are subject to it in varying degree. 

 I all it presents the characters of a cellular local 

 /ergrowth of some part of the body, growing pro- 

 essively till it destroys life. A mountain of paper 

 IS been covered with descriptions of the details of 

 .e structure of cancer, its naked-eye appearances, 

 le course of the disease, and numerical tables of its 

 equency in successive years in all countries. It 

 3uld be futile to attempt a summary even of the 

 lient facts embodied in all this recorded experience 

 ithin the limits of the present essay, which must be 

 stricted to a statement of the central problem, the 

 mel of cancer research, as it appears to the writer. 

 As a preliminary, some elementary facts of the struc- 

 re and life-history of living things must be touched 

 >on. Underlying the diversity of appearance and 

 mplexity of the bodies of the higher animals (to 

 lich it is convenient to restrict ourselves), there is 



surprising uniformity of structure. Skin, bone, 

 ood, brain, liver, and intestines, all are made up of 

 cells," microscopic in size, differing in detail, but 

 I built on the same plan. In the warm-blooded 

 imals like ourselves their size is such that, placed end 

 end, from 1,000 to 3,000 will lie in the space of an inch, 

 ley are of a semi-fluid or watery consistence, and in 

 ch there lies a denser spherical body, the nucleus, 

 le surrounding clear substance is termed protoplasm, 

 d with the nucleus is the repository of the processes 



life. Masses of ceUs of the same kind are called 

 sues — e.g. nerve tissue, epithelial tissue (covering 

 e surface of the body and lining the intestines), 

 ascular tissue, and so forth. The organs of the body, 

 ch as the brain, the heart, the liver, are made up of 

 number of tissues modified and arranged for the 

 )rk they have to do. Careful measurements have 

 en made of the cells of corresponding tissues from 

 mts and dwarfs, and their sizes have been found to 



the same. The difference in size of the individuals 

 question is therefore due to the greater number of 

 lis in the body of the giant. The same holds good 

 : the tissues of cliildren and adults : their cells 

 E of nearly the same size, but there are more of them 



in the adult. Similarly the corresponding cells of 

 a rat and a horse are nearly of the same size, and they 

 are correspondingly more numerous in the larger 

 animal. 



How is this uniform size of the cells maintained 

 whUe their number increases ? In the simplest manner 

 imaginable. If we examine the cells of the liver of 

 a new-born mouse, we find that in a considerable 

 number the central spherical nucleus has divided into 

 two, and then a constriction appears in the surrounding 

 protoplasm. The constriction gradually deepens till 

 the cell is cut quite through, and two cells, each half 

 as large as the original, result. In a growing animal 

 the two daughter cells produced in this way rapidly 

 increase in size, till they are as large as their prede- 

 cessor, when the process is repeated. This alterna- 

 tion of di%'ision of cells, and increase of the daughter 

 cells to the previous size, is the universal mode of 

 growth in the higher animals. As everyone knows, 

 the process is more rapid in the young. A child 

 which weighs seven pounds at birth may be three 

 times as heavy at the end of the first year of life. 

 As age advances the process slows down, and a time 

 arrives when the size becomes constant, and we say 

 that growth has ceased. Careful and minute study 

 of the cells of adult men and animals shows, however, 

 that cell-division is still going on in many of them. 

 This is usually regarded as a provision for replacing 

 cells worn out or damaged in the business of life. 

 From another standpoint it may be regarded as a 

 slower continuation of the growing process which is 

 so obvious in early life. In extreme old age it becomes 

 still slower, and is no longer adequate to keep up the 

 size of the body. The very old seem to shrink in 

 bulk and stature, and when the failure reaches some 

 organ essential to life, such as the muscular tissue of 

 the heart, life sinks to its final ebb. 



Two remarkable properties of the living body lessen 

 the similarity which this sketch conveys of machine- 

 like regularity, as of a watch wound up and allowed to 

 run down. The individual cells of the various tissues 

 are not independent, self-contained units, each going 

 its own way. They are subject to a general controlling 

 influence, the nature of which is still obscure, which 

 limits their rate and amount of growth, so that a fairly 

 uniform proportion is maintained between the different 

 organs and parts of the body. The reality of this 

 regulating mechanism is also shown by the fact that 

 the different animal species (and even the smaller 

 racial groups), each attain a characteristic average 

 size. The rat, the lion, the terrier, and the mastiff, 

 will occur to everyone. In the same way sheeps' 

 hearts or kidneys are always pretty much of a size, 

 and smaller than the corresponding parts of the ox. 

 We shall see that a failure of this controlling in- 



