THEORIES AND PROBLEMS OF CANCER 237 



nearly balanced, as they are in the experiments under review. 

 What was said in the last article with regard to these graftable 

 mouse cancers having acquired some of the characters of 

 separate individuals not possessed by primary malignant 

 growths through the process of selection necessarily involved 

 in their propagation must also be borne in mind. 



Neuberg and his collaborators attribute the failure of sub- 

 cutaneous injections to the other tissues having broken down 

 the unstable compounds they used before the tumour cells 

 were reached. The explanation with regard to the contraction 

 of the blood-vessels that I have just suggested seems to be as 

 satisfactory upon this point, as whilst contraction of the vessels 

 would probably be produced, though more slowly, by the 

 subcutaneous injections, the fluid would not be in the actual 

 blood stream from the moment of its introduction into the 

 system and so would not have a chance of being concentrated 

 immediately in the tumour. 



Wassermann describes amorphous particles of selenium and 

 Neuberg and his collaborators amorphous particles of the 

 metals which were used as being discernible under the micro- 

 scope in the tumour cells. As the " compounds " they used 

 are described as very unstable they would probably break down 

 in any part of the body but being in greater quantity in the 

 tumour when first introduced more breaking down should 

 take place there than anywhere else. 



A definite claim has been made recently to the successful 

 treatment of cancer by intravenous injections of colloidal 

 selenium. 1 As far as I know, only one or two cases have 

 been treated in this manner, so that even a disappearance of 

 the tumours would mean no more than that there was no 

 direct evidence against the disappearance of the tumours being 

 connected with the injection of the selenium in the colloidal 

 form. I have tried colloidal selenium upon a number of mice 

 and rats bearing malignant tumours produced by grafting. No 

 effect was produced upon the tumours whether the colloid was 

 used alone or in conjunction with eosin. It is noteworthy that 

 whilst all the salts of selenium and combinations of selenium 

 and eosin which I have tried are very highly toxic, minute 

 doses killing mice or rats in a few minutes, selenium in the 

 colloidal form is not at all poisonous. 



1 Societe Medical des Hopiteaux de Paris, February 14 and March 1, 191 2. 



