112 THE BLOOD AND THE LYMPH 



could ever occur. Certain observers, however Morawitz, for example 

 lay great stress on this as an important factor in hemorrhagic diseases. 



4. An excess of cmtithrombin. The undoubted increase in this substance 

 that can be brought about experimentally by injecting hirudin or pep- 

 tone into animals, has stimulated careful search for a similar increase in 

 the blood in clinical conditions in which abnormal blood clotting is one 

 of the symptoms (Whipple 10 ). Antithrombin is said to be increased in 

 septicemia, pneumonia, miliary tuberculosis, etc. 



5. A deficiency of calcium ions. Although at one time it was supposed 

 that this might be responsible for the feeble clotting in hemophilia, it 

 has not been found, after very extensive trials, that the exhibition of 

 Ca salts in any way relieves the condition. It is said, however, that the 

 slow coagulation seen in obstructive jaundice is decidedly shortened by 

 treatment with calcium salts. 



One thing stands out prominently in connection with the whole problem, 

 and that is the close relationship of the blood platelets to the clotting 

 process. From these cells are derived, according to Howell, not only the 

 prothrombiri but also, as from other cells, thromboplastin. It is not sur- 

 prising therefore to find that decided alterations in the platelet count 

 occur in cases of faulty blood clotting, and that local accumulations of 

 these elements within the blood vessels, produced by their clumping to- 

 gether or agglutinating, is followed by a formation of local clots, as in 

 thrombosis. 



Hemorrhagic Diseases 



In many of the so-called hemorrhagic diseases (acute leucemia and 

 aspastic anemia) and in the hemorrhagic varieties of diphtheria and 

 smallpox, the platelet count drops from its normal of between 200,000 

 and 800,000 per cubic millimeter to well below 100,000, and indeed in 

 these conditions it is frequently difficult to find any platelets. Samples of 

 blood clot outside the body within the normal time, but the clot is soft 

 and usually fails to retract in the normal manner. It is on account of 

 this, rather than slow clotting that the hemorrhage continues, so that in 

 appraising the gravity of the symptom it is best to measure not the clot- 

 ting time but the time that it takes for bleeding to cease from a small 

 skin wound, as in the lobe of the ear. This can be very accurately done 

 by applying blotting paper at regular intervals to the puncture (Duke 17 ). 



The most interesting and at the same time the most mysterious of all 

 conditions in which blood clotting is interfered with is hemophilia. The 

 clotting time is longer than normal, but even after the clot forms, bleed- 

 ing is likely to continue because the clots are very readily displaced. Both 

 clotting time and bleeding time are increased. So far no change in the 



