280 



LECTURES ON IMMUNITY 



serum be taken as a unit, this may be regarded as nearly 

 equivalent to the quantity of calcium present,. if it does not 

 exceed a certain limit ; now n equivalents of pseudo-globulin 

 are added, then at equilibrium we have (n x) equivalents 

 of pseudo-globulin, (i x) equivalents of calcium para- 

 caseate, x equivalents of calcium salt of the pseudo-globu- 

 lin, and (a + x) equivalents of para-casein, where a is the 

 quantity of free para-casein for n = o. Then the equi- 

 librium follows the equation 



(n- x)(\- x) = K-x(a+x). 



If a is high, i.e. in the presence of much casein, we may 

 regard (a + x) as a constant, and we have the equation with 

 the aid of which the calculated values above have been 

 derived. We may therefore say that the opinion of Fuld 

 and Spiro agrees with the experiments, and it is easy to see 

 how these might be controlled to a still higher degree. 



Even against the coagulation of blood-plasma there exist 

 some natural antibodies, one of which, the hirudin, the 

 extract of leeches, has been known for a long time. Fuld 

 and Spiro l made the following determinations of the quan- 

 tity of "free muscle extract" from goose, of which 0.4 c.c. 

 had been taken, in the presence of n c.c. of an extract of 

 leeches, acting on i c.c. of goose plasma. 

 NEUTRALISATION OF MUSCLE EXTRACT FROM GOOSE BY MEANS OF HIRUDIN 



1 Fuld and Spiro: Hofmcisters Beitrage^ 5. 181 (1904). 



