WHAT MEDICINE HAS DONE AND IS DOING FOR THE RACE 449 



(1722- 1 809) neglected discovery of percussion and R.T.H. 

 Laennec (1781-1826) in 1819 published his classical work on 

 auscultation. The alterations of the heart sounds (murmurs) 

 which characterize valvular disease were elaborated through- 

 out most of the nineteenth century, and, as is now apparent, 

 attention was directed too much to the more obvious 

 evidence of valvular disease and not sufficiently to the condi- 

 tion of the muscular efficiency of the heart. The signs of 

 cardiac disease were regarded as far more important than 

 the patient's symptoms and sensations. The new cardiology 

 began with James Mackenzie's (1853-1925) elucidation of 

 the irregularities of the pulse, and the more accurate indica- 

 tions for the use of digitalis in cardiac affections, derived 

 from instrumental investigation; this advance was con- 

 tinued by Thomas Lewis' observations with the electrocardi- 

 ograph. By these means the actual changes in the heart 

 revealed by special methods were correlated with more 

 obvious signs; the latter have thus in most instances be- 

 come a reliable guide to the underlying condition without 

 recourse to the more elaborate methods of the original pio- 

 neers. More accurate knowledge of the causes of heart 

 disease, such as acute rheumatism, infections and especially 

 syphilis have made curative treatment more rational and 

 successful, and prevention more possible. The accurate 

 instrumental estimation of blood pressure which enables its 

 abnormal characters to be detected before symptoms have 

 made their appearance, is most valuable as a warning to 

 start preventive treatment in an early stage. 



A brief reference should be made to the advances made 

 in the recognition and treatment of the various diseases oj 

 the blood-forming organs. Anemia may be due to many causes; 

 one form is due to the presence of a parasite in the alimentary 

 canal, as in hookworm disease (see p. 442) ; the destruction of 

 these worms or better the prevention of this infection is the 

 logical and successful sequel of this new knowledge. Another 

 form of grave anemia, the pernicious or Addisonian, has now 

 been shown to be benefited by an administration of liver 

 substance which also has a most satisfactory influence 

 on the tropical disease known as sprue. Anemia due to loss of 

 blood, such as occurs as the result of disease, wounds or 



