316 PHYSICAL PROPERTIES 



Bradley and Sansum (8) believe that the haemoglobins from 

 different animals are antigenically different because guinea-pigs 

 sensitized to ox or dog haemoglobin failed to display anaphylactic 

 shock or reacted but slightly to haemoglobins of other origins, 

 while they reacted strongly to the haemoglobin with which they 

 were sensitized. As the haemoglobin preparations employed by 

 Bradley and Sansum were admittedly (with the exception, 

 they believe, of the dog haemoglobin) not free from contamina- 

 tion by serum the interpretation of these results is open to serious 

 question. Doubt is especially thrown upon this evidence for 

 the specificity of haemoglobins from different species by the fact 

 that the animals sensitized to the purest preparation of haemo- 

 globin employed, that of the dog, reacted strongly not only to 

 to dog haemoglobin but also to dog serum. Having regard to the 

 investigations of Wichmann and Katz, cited above, revealing 

 the marked ability of crystalline proteins to absorb the menstruum 

 from which they are deposited, and to the observation of Schulz 

 and Zsigmondy (95) that egg albumin must be recrystallized 

 from 3 to 6 times in order to remove appreciable contamination 

 by other proteins, we may infer that in all probability the speci- 

 ficities demonstrated by Bradley and Sansum are serum-speci- 

 ficities and not haemoglobin-specificities. 



According to Howell (43), fibrin must now be added to our 

 list of crystallizable proteins. He finds that when fibrinogen is 

 precipitated by thrombin, the fibrin, in media of normal H+ 

 concentrations, separates out in crystalline needles readily recog- 

 nizable as such under the ultramicroscope. They vary in length 

 from 10 to 30 microns and form a close mesh-work. The normal 

 blood-clot is therefore a crystalline gel. The blood of inverte- 

 brates, however, yields a non-crystalline gel and a similar gel is 

 yielded by mammalian fibrin in alkaline media. Such non- 

 crystalline gels, however, fail to display the spontaneous con- 

 traction or "synaeresis" which is so characteristic of normal 

 blood-clots. 



LITERATURE CITED 



(1) van Bemmelen, J. M., Zeit. f. anorg. Chem. 13 (1896), p. 233; 18 



(1898), p. 14. 



(2) Berczeller, L., Biochem. Zeit., 53 (1913), p. 215. 



(3) Beutner, R., Biochem. Zeit., 39 (1912), p. 284; 48 (1913), p. 217. 



(4) Bogusky, J. G., Ber. d. d. chem. Ges. 9 (1876), p. 1646. 



