300 DLSTCRliAXCIJS OF CIRCCLATION 



especiallj" clearly by the observation of Ledingham and Bedson ^^ 

 that anti])lat('let seruiu will ])rotliice a ]Mir]nirie condition when 

 injected into animals of the species furnishing the platelets, al- 

 though no similar effect is produced by antileucocyte or antiery- 

 throcyte serum. Hess^- states that there may be an hereditary 

 jiurpura, sometimes occurring in the females of hemophilic families, 

 differing from hemophilia in a deficiency in the number of platelets, 

 hemorrhages following local congestions or puncture wounds and 

 exhibiting an increase in the bleeding time. 



ANEMIA AND THE SPECIFIC ANEMIAS ^^ 



The customar}^ division of the anemias is into — (a) priinary, i. e., 

 those in which the anemia seems to depend upon some abnormality in 

 the blood-forming organs or in the blood itself; and (&) secondary, 

 embracing anemias the result of some obvious cause, such as hemor- 

 rhage, poisoning with blood-destroying poisons, cachexia, etc. In 

 these various forms of anemia certain chemical differences prevail, but 

 they are by no means so striking as are the histological differences in 

 the formed elements of the blood. ^* 



SECONDARY ANEMIAS 



As the simplest variety, anemia following a single large hemorrhage 

 may be considered first. 



If loss of blood by hemorrhage is rapid, the effects are naturally 

 much more serious than when the loss is slow. The total quantity' of 

 blood in the average adult is estimated at about ]{r, to ^i.j the total 

 body weight (therefore about 10 to 12 pounds), although this pro- 

 portion does not hold for extremely obese or extremely thin indi- 

 viduals; ^^ in infants the proportion is lower — about ^20- When one- 

 third of the total amount of blood is lost rapidly, a marked fall of 

 blood pressure occurs; loss of one-half of the total amount may be 

 fatal, and loss of more than that at one time usually is fatal. The 

 chief cause of death following large hemorrhages is the low blood 

 pressure rather than the loss of any of the constituents of the blood ; 

 hence the successful results of the use of physiological salt solution 

 after severe hemorrhage. The number of corpuscles may be greatl.v 

 reduced after several small hemorrhages, even to as low as 11 per 

 cent, of the normal number (Hayem), without fatal results, because 

 in the intervals between the hemorrhages enougli fluid lias been taken 

 up b}' the blood to maintain the blood pressuiv within safe limits. 



31 Lancet, Fcl). l."?. 101.5. 



32 Arch. Int. Med., 1!)1() (17), 203. 



33 M(.(abolism in anemia reviewed I)v ^lolir, nandbucli d. Bioclioni., liUO ( I\' 

 (2) ), 372. 



34 Concerning local anemia, see "Infarcts." 



35TIaldane and Smith (Jour, of Physiol., 1000 (25), 331) estimated tiie blood 

 of adults at but J^q "f ^'"' 1>o(l.v weiglit. 



