298 DISTURBANCES OF CIRCULATION 



or tissue-cells. Consequently the blood is acted upon very slowly 

 by the enzymes liberated by the leucocytes it contains itself, and by 

 the small amounts of proteases in the serum. Furthermore, the prod- 

 ucts of decomposition are not soon absorbed, but accumulate in con- 

 siderable amounts, so that we often find crystalline deposits of 

 hematoidin, sometimes even of hematin, hemoglobin, or parahenioglobin 

 (Nencki)^^ or methemoglohin. 



The least soluble constituent of the red corpuscle stroma, choles- 

 terol, also accumulates in such extravasations as large, thin plates; 

 after most of the other products of disintegration have been absorbed 

 from such accumulations of blood, the most conspicuous part of the 

 residue may be a mass of cholesterol crystals imbedded in prolifer- 

 ating connective tissue. 



Hemophilia" 



There are several pathological conditions associated with increased 

 tendency to bleeding, notably scurvy and the various forms of pur- 

 puras, but especially the remarkable hereditary condition, hemophilia. 

 In the purpuric diseases various of the factors concerned in coagula- 

 tion of the blood have been found altered, ^^ notably the blood plate- 

 lets,^^ but Howell found no change in either prothrombin or anti- 

 thrombin in yurpura hemorrhagica and other related conditions. Simi- 

 lar negative results were obtained in scurvy by Hess.^° Melena 

 neonatorum exhibits decreased prothrombin in the blood, while in 

 leukemias and anemias there may.be an excess of antithrombin,^' 

 leading to severe hemorrhage (see also Thrombosis). 



Since hemophilia seems, superficially at least, to depend upon some 

 alteration in a chemical property of the blood, namely, coagulability, 

 it is frequently regarded as an example of hereditary transmission 

 of a chemical abnormality. The exact cause of this peculiar tendency 

 to prolonged bleeding from insignificant or perhaps imperceptible 

 wounds has been sought vigorously by both histological and chemical 

 means, but as yet without avail. Various observers have described 

 abnormal thinness, or increased cellularity or fatty degeneration of 

 the vessel-walls, but the findings have been far too inconstant to 

 afford a satisfactory anatomical explanation of all the features of 

 hemophilia. Likewise increased blood pressure can be ruled out, for 



3" Arch. exp. Path. u. Pharni., 1S8G (20), 332.^ 



" Ijiterature and r6suin6 given bv Stenipcl, Cent. f. Grcn7,p;eb. Med. u. Chir., 

 1900 (;i), 75;i; Sahli, Zeit. f. klin. Med., 1<)05 (5(>), 29-4; Marcliand, in Krehl and 

 Marchand's Handb. allg. Pathol., 1912, II (1), 307. Also later references in this 

 text. 



^^ See Ilurwitz and Lucas, Arch. Int. Med., 191G (17), 543; Minot et al, ibid., 

 191(5 (17), 101. 



'"See Lee and Robertson, Jour. Med. Res., 1916 (3;j), 323; Hess, Proc. See. 

 Exp. Biol. Med., 1917 (14), 96. 



^0 Ainer. .Jour. Dis. Children, 1914 (8), 386. 



" Whipple, Arch. Int. Med., 1913 (12), 037. 



