THE STUDY OF CANCER 21 



As I pointed out on a previous page, the cancer cells acquire at 

 each transference a specific stroma, the connective tissue 

 reaction they call forth in the host. A culture of isolated cells 

 has not been obtained, since growth always proceeds in the 

 form of a tissue with intimate vascular supply. We emphasised 

 the distinction thus revealed between the cells of different 

 growths nearly allied histogenetically, and the parallel it 

 presented to the biological reactions whereby blood relationship 

 has been established. At the same time we pointed out its far 

 greater delicacy. In what I have briefly outlined with regard 

 to protection the same delicacy, or specificity, appears. The 

 cancer cell is dependent on the provision by the host of a 

 connective tissue and vascular reaction, if it is to grow into 

 a tumour. It would appear to be a piece of short-sighted 

 generosity on the part of the host to supply connective tissues 

 to subserve merely the needs of the greedy cancer cells, and yet 

 this appears to be the relation which subsists when a tumour is 

 growing well. The question arises, is the connective tissue 

 reaction supplied only in response to the needs of the cancer 

 cells, or is it really protective, as in the case of the similar 

 reactions elicited by the tubercle bacillus or other organisms? 

 When a tumour undergoes spontaneous absorption, the 

 connective tissue reaction does become protective, and the 

 acquisition of phagocytic properties by its cellular elements is 

 the main factor in removing the remains of the tumour. Thus 

 under certain conditions the organism is certainly capable of 

 defending itself very actively through reaction to the presence 

 of the cancer cells, and after the process remains protected. 

 The conclusion that phagocytosis is the only agency by which 

 protection is conferred would in my opinion be unwarranted 

 at present. Spontaneous absorption appears to be frequently 

 associated with a phase of depressed growth of the tumour 

 cells themselves. We do not yet know exactly whether the 

 cancer cells require to undergo changes — either spontaneous, 

 or induced from the side of the host — placing them at times at 

 the mercy of the connective tissue which, at other times, appears 

 to be their willing servant. When a graft is introduced into 

 a protected mouse, little, perhaps no, proliferation follows, and 

 the tissue speedily dies. Whether it is killed by the fluids of 

 the body, or simply starved to death, because it is prevented 

 from exercising its chemiotactic influence on the connective 



