23 6 SCIENCE PROGRESS 



was concentrated in the tumour. These facts seem to suggest 

 that the action of the preparations under consideration may 

 possibly be to some extent mechanical and not due to any 

 selective action upon the tumour cells. We have seen that 

 there is no nerve supply to malignant growths. The dilatation 

 and contraction of blood-vessels is controlled by the nerves 

 and hence it is possible that when these poisonous substances 

 are introduced into the circulation the immediate result is the 

 contraction of the blood-vessels generally, excepting of course 

 those in the tumours, through their action upon the nervous 

 system. The blood-vessels and spaces in the tumour, owing 

 to the increased pressure produced by the contraction of the 

 vessels of the body, are forcibly dilated. The poisonous com- 

 pounds having been introduced directly into the blood stream 

 would thus act far more upon the tumour cells than upon 

 those in the body generally and as they are described as being 

 very unstable they would break down before the blood-vessels 

 of the body dilated. The fact that the doses that are effective 

 in producing the destruction of the tumour are so very nearly 

 those that result in the death of the animal is very suggestive 

 in view of this explanation. So is also the fact that though 

 it is reported that in the very few cases of spontaneous tumours 

 in animals upon which these preparations have been tried, 

 effusions of blood and softening have occurred more often than 

 not, no cures have been obtained. The animals have always 

 died before the tumour was destroyed. 



As was explained in a previous article, the tumours pro- 

 duced in mice and rats by grafting become surrounded by a 

 capsule of inflammatory tissue before cell proliferation begins 

 among the tumour cells, so that these tumours are cut off from 

 the body of the animal in which they grow in a manner not 

 found to happen in a spontaneous primary cancer. This would 

 very probably, to a certain extent, confine the poisonous com- 

 pound to the tumour after it had been concentrated there 

 through the contraction of the blood-vessels of the body gener- 

 ally and the concomitant dilatation of the blood-vessels and 

 blood spaces of the tumour. That the blood-vessels of spon- 

 taneous tumours should become dilated in the same way is 

 what might be expected but in such cases there is lacking 

 that isolation of the tumour cells which forms so useful a 

 factor in success when the curative and lethal doses are very 



