PREFACE XV 



Botanical Department at the University of Liverpool. 



It was when experimenting with a mixture of 

 polychrome stain, extract of haemal gland, and atropine 

 that I saw mitotic figures in lymphocytes for the first 

 time in May, 1909; and the. ensuing months were 

 occupied in the investigation of the cytology of these 

 cells and of the means whereby they might be induced 

 to reproduce themselves. It was not until October, 

 1909, however, that I was able to induce divisions in 

 polymorphonuclear leucocytes. In December, 1909, I 

 discovered almost accidentally that extracts of dead 

 tissues, if they were allowed to decompose by the 

 action of putrefactive bacteria, would, by themselves, 

 induce the division and multiplication of lymphocytes, 

 and this was followed by the investigation of the 

 action of "globin" in January, 1910. In February, 1910, 

 while investigating the epithelial cells present in some 

 vaginal secretion, it occurred to me to try to induce 

 divisions in them, and this experiment has been suc- 

 cessful in the case of one or two cells. 



In April and May, 1910, when working with my 

 assistant, Dr. Cropper, I saw divisions induced by 

 kreatin and xanthin, the "extractives" contained in the 

 remains of dead tissues; and we then also investigated 

 the augmenting action on cell-division of the alkaloids 

 choline, cadaverine, etc., produced by the decompo- 

 sition of putrefaction. These points led me to elaborate 

 the theory regarding the cause of cancer which is 

 described in the latter part of this book. 



The dates of the treatment of the two cases of 

 cancer are given in the description of them which 



