378 SCIENCE PROGRESS. 



tirely unable to corroborate Lowit's statement. Schmidt's 

 view of the preponderating influence ofleucolysis on blood- 

 clotting is therefore not borne out. 



I should like to add in conclusion that, although I 

 regard Pekelharing's attempt to harmonise rival theories as 

 extremely ingenious, it appears to me to break down in two 

 points. The first of these is his idea that nucleo-albumin is 

 the mother substance of fibrin-ferment, and convertible into 

 fibrin-ferment by the action of a calcium salt. His experi- 

 ments do not bear this out thoroughly, for the amount of 

 calcium salt is presumably the same in extravascular as in 

 intravascular blood. Yet nucleo-albumin causes coagulation 

 in one, but not in the other. 



The second point is his inclusion of fibrin-ferment among 

 the nucleo-albumins ; there is no analytical evidence of this. 



It is quite possible that nucleo-albumin and fibrin- 

 ferment are related substances, perhaps related very closely. 

 It is also quite possible that they are absolutely different 

 substances. There certainly are differences : let me 

 enumerate some. 



a. Fibrin-ferment is not readily coagulated by alcohol ; 

 nucleo-albumin is. 



b. Fibrin-ferment cannot be obtained by Schmidt's 

 method from nucleo-albumin. 



c. Fibrin-ferment causes coagulation in extravascular 

 (salted) plasma ; nucleo-albumin does not. 



d. Nucleo-albumin causes coagulation in intravascular 

 blood ; fibrin-ferment does not. 



These last two differences form one of the greatest 

 difficulties in properly understanding the method of fibrin- 

 formation, or at least of reducing it to one common law. 



Why, after all, is there a need for a common law ? May 

 not the two substances in question be quite distinct from 

 each other, each being capable of producing fibrin under 

 suitable conditions ? 



It is by no means inappropriate to close a paper on such 

 a subject as blood coagulation with a number of unanswered 

 questions. 



W. D. Halliburton. 



