THEORIES AND PROBLEMS OF CANCER 235 



portion on cells and nucleoproteids from normal tissue. These 

 experiments however, as far as I know, have not been repeated. 

 Neuberg and his collaborators apparently assume that the 

 peculiar characters of rapid growth and degeneration which 

 they attribute to the cells of malignant growths are due to the 

 presence in them of these abnormal enzymes; their object has 

 been to produce some substance which will act only or to a 

 greater extent in the presence of the enzymes in question and 

 increase the degeneration to such an extent that all the tumour 

 cells will be destroyed. They have worked with compounds 

 of cobalt, silver, copper, platinum, gold and tin, obtaining the 

 best results with compounds of the first two. While claiming 

 that definite effects were produced upon the tumour cells by 

 hypodermic injections, they say that they did not effect actual 

 cures until they used intravenous injections. 



In the case of these experiments, as in Wassermann's, the 

 tissues are described as undergoing degeneration, softening, 

 liquefaction and final disappearance. The useful dose of the 

 compounds is nearly as great as that which kills the animal 

 outright and must be injected into the circulation directly. 

 This latter point adds to the difficulty of the experiments, as 

 it is exceedingly difficult to inject a fluid into a vein in a mouse ; 

 moreover, as the operation has to be repeated frequently and 

 the difficulty is increased rather than diminished upon each 

 occasion, the experiment in each individual case may have 

 to be abandoned before completion. It is also to be regretted 

 that none of these investigators has given any definite informa- 

 tion either as to the constitution or as to the manner of 

 preparing the " compounds " they used, so that their experi- 

 ments cannot be confirmed nor is any kind of check upon them 

 possible ; nor can the work be carried on by other investigators 

 along varying lines from the new standpoint, as it probably 

 would be if the results they have recorded were confirmed. 



The immediate effect of the "compounds" injected by 

 Neuberg and his collaborators is described as a contraction of 

 the blood-vessels of the body and a dilatation of those of the 

 tumour. This dilatation is so great that extravasations of blood 

 visible to the naked eye are numerous. In Wassermann's ex- 

 periments the injection of the selenium-eosin preparation was 

 described as turning the mouse pink all over immediately but 

 the pink coloration disappeared rapidly from the body and 



