448 HUMAN BIOLOGY 



been prepared, and in the meanwhile much has been done; 

 conditions which favor the incidence of cancer, such as 

 chronic irritation and inflammation, have been recognized 

 and so can be obviated, such as irritation of the tongue 

 by a sharp tooth or of the skin by materials such as soot, 

 paraffin and other agents in industrial occupations. To take an 

 example in which medical men have been the main sufferers: 

 more than a hundred radiologists have now died from cancer 

 of the skin caused by x-rays; standardized methods of 

 protection against the dangers of x-rays and radium expo- 

 sures have now been formulated, so as completely to obviate 

 them. 



Educative campaigns to instruct the pubHc about the 

 importance of seeking medical advice about the earliest 

 symptoms of possible mahgnant disease, so that if present a 

 growth may be removed at a period when cure can be 

 obtained, have done much good. The progress of diagnostic 

 methods, such as x-rays, enabling a decision to be made at 

 a stage not previously possible, has given the sufferers the 

 benefit of cure by early operation; the improvement of 

 surgical technique and x-ray and radium therapy are other 

 advances which have been of service in the treatment 

 of cancer. Before 1890 the operative removal of tissues and 

 lymphatics around malignant tumors was not sufficiently 

 wide, and as a result recurrences were more frequent than 

 after the more complete and extensive operations now 

 performed. 



One of the great triumphs of applied physiology was the 

 exact localization of tumors in the brain so as to indicate 

 the exact position where the surgeon should trephine the 

 skull for their removal. 



Diseases oj the Heart and Blood Vessels. Except aneurysm, 

 or pathological dilatation of the arteries of the limbs with 

 a tendency to rupture which was known to Galen (130-200 a. 

 D.), little in connection with the circulatory system was 

 recognized until long after Harvey's publication of the 

 circulation of the blood (1628). The reason for this was that 

 the methods of physical examination of the heart were not 

 practised until the beginning of the nineteenth century when 

 J.N. Corvisart (1755-1821) in 1 808 resuscitated Auenbrugger's 



