T2o THE POPULAR SCIENCE MONTHLY 



portant the methods of immunology are, for here we have a disease 

 which, as the result of the application of such methods, is definitely 

 placed among the transmissible diseases and is given a satisfactory 

 theory for prophylaxis in spite of an utter absence of knowledge con- 

 cerning its causal agent. An analogy is seen in yellow fever, the micro- 

 organism causing which we do not know and for which we have no 

 specific treatment, but which is controlled simply through our knowl- 

 edge of its transmission by the mosquito. 



While on the subject of Flexner and his work mention must be made 

 of the most important contribution in recent years to our list of curative 

 sera, the antimeningococcus serum. The production of this serum, 

 which in the best form is the result of the labors of Flexner and his as- 

 sociates, is an accomplishment which, in reducing enormously the mor- 

 tality of epidemic meningitis, is in itself a sufficient justification for the 

 establishment of the Rockefeller Institute. The beneficial results of its 

 use are very definite and the mode of its administration, by direct in- 

 jection into the spinal canal, has been of great value in emphasizing the 

 importance of the local treatment of localized infections. 



Many other phases of activity in the field of immunity might be 

 presented, but this brief and disconnected summary will, I hope, suffice 

 to indicate something of actual accomplishment in this field, the main 

 lines of present endeavor, and the many opportunities for future 

 achievement. Much of present-day effort may not lead immediately to 

 tangible results — an outcome not uncommon in medical research — but 

 the volume of work in progress and the vigor with which it is being 

 prosecuted promises ultimately the solution of the many problems of 

 the infectious diseases. 



The Investigation of Cancer. — In no field of medical science has the 

 modern experimental method given greater results in a few brief years 

 and offered greater promise for the future than in the study of that 

 fatal and obscure disease, cancer. Owing to the brilliant initiative of 

 Jensen in Denmark and Leo Loeb in this country, it has been shown 

 that a form of cancer occurs in certain lower animals, particularly in 

 rats and mice, that can be artificially transmitted from one animal to 

 another of the same species. This fact has afforded a means of study- 

 ing in detail the method by which a malignant tumor grows in the 

 body and more particularly has thrown light on the resistance or im- 

 munity to tumor growth which may occur naturally in certain individ- 

 uals and which may even be artificially produced. Scattered over the 

 world are small groups of individuals, more particularly in England, 

 in Germany and in America, who are devoting their entire energies to 

 the solution of this problem. From several divergent sources have come 

 published results of experiments which offer the greatest promise that 

 we may soon learn a method of curing these tumors. Alreadv Ehrlich 



