THE BLOOD. 543 



of which we merely know that it is closely related to the globulins, and 

 fibrin also belongs to the proteins. It is perfectly possible that fibrinogen 

 consists of several molecules of fibrin which take up water and disintegrate, 

 whereby eventually fibrin is formed, so that although fibrin is formed from 

 fibrinogen, the coagulation is essentially a hydrolytic decomposition. 

 There are no facts known at present which contradict such an assumption. 

 Under ordinary conditions when the body is wounded, the blood flows 

 out from the blood-vessels past the tissues. Its clotting is thereby accel- 

 erated. We must here consider the anomalous behavior of the blood in 

 hemophilia. This condition is especially characterized by the fact that the 

 blood does not clot readily. Even from the slightest wounds there is a 

 tendency to bleed freely. There may be even such a slight tendency 

 for the blood to clot, that a wound resulting, for example, from the 

 extraction of a tooth may cause the patient to bleed to death. Hemo- 

 philia has been of interest to biologists not only on account of this peculiar 

 condition but also by a further peculiarity which holds almost invariably. 

 This is the fact that it is hereditary, and, moreover, it is almost always 

 the male members of the so-called families with hemophilic blood, who 

 inherit this tendency. On the other hand, the female members of the 

 families alone transmit the anomaly. The following tree shows how this 

 tendency runs : 



Family I 1 



If I I, If 



9 9 9 9 



(47yrs.old) | F "I/ I 26yrs.old | 13yrs.old 



I $ $ 9 t 



9 (19 yrs. (15 yrs. (12 yrs. (4 yrs. (1 yr. 



15 yrs. old) old) old) old) old) 



old 



The symbol $ indicates those male descendants which were normal, 

 indicates those males having the tendency to bleed freely, and 9 rep- 

 resents the female members of the family. We mention hemophilia at 

 this place because this anomalous behavior, which is hardly to be regarded 

 as a disease, inasmuch as the individuals are normal in every other respect, 

 ought to be of assistance to us in the study of the coagulation of blood. 



1 Abderhalden: Beitrage pathol. Anat. und allgem. Path. 35, 213 (1903). See 

 Stahel: Inaug. Dissert. 1903, Zurich, 1880. Hoessli: Inaug. Dissert. Basel, 1885. Sahli: 

 Z. klin. Med. 56 (1905). 



