viii PRECIPITINE-REACTION AND GOLD NUMBER 333 



albumin yields only one, while euglobulin and pseudo-globulin yield 

 three each. The serum of animals which have been injected does not 

 develop its full precipitating power till five days after the injection 

 (Nuttall, Hunter), and the amount of precipitin in the serum is always 

 in inverse ratio to the number of leucocytes. It is suggested that 

 the precipitins are formed in the leucocytes, and Kraus and Levaditi l 

 are likewise of the opinion that leucocytes give rise to the precipitins. 



Meyer 2 has found that extracts from mummy-muscles, 2000-5000 

 years old, gave distinct precipitates with the serum of rabbits, which 

 had been injected with fluid from human pleural transudations, 

 placental blood, or ascitic fluid, while no precipitates were formed in 

 the control experiments. 



Merkel 3 found that rabbits which had been injected with human 

 blood, on becoming pregnant, passed on the precipitins to their 

 offspring, and that therefore the young rabbits reacted in the same 

 way as did their mothers. 



5. The Gold Number of Albumins 



Zsigmondy having found that a colloidal gold-solution is precipi- 

 tated by electrolytes, e.g. by NaCl, but that this precipitation is 

 influenced by the presence of other colloids in a manner which is 

 quite characteristic for each colloid, this question was more fully 

 investigated by Schulz and Zsigmondy. 4 



They designated that number of milligrammes of a colloid which 

 is just insufficient to prevent 10 ccm. of a colloidal gold-solution from 

 showing a change in colour, after the addition of 1 ccm. of a 10 per 

 cent NaCl solution, the gold number of the colloid in question. 

 Schulz and Zsigmondy have determined these gold numbers for the 

 albumins of egg-white : 



Globulin .... "02-0 '05. 



Ovomucoid . . . , 0'04-0-08. 



Crystalline egg-albumin . . 2-8. 



Other (con-)albumin . . . 0'03-0'05. 



Alkali-albuminate . . . 0'006-0'04. 



The great difference between the crystalline egg-albumin and the 



other colloids of egg-white makes it possible to recognise very minute 



traces of impurity in the egg-albumin with greater precision than by 



any other method. This method has shown that egg-albumin must be 



1 Kraus and Levaditi, Compt. Rend. 138. 865 (1904). 



2 J. Meyer, Milnchener med. Wochensch. 1904, p. 663. 

 :{ H. Merkel, ibid. 51. No. 8 (1904). 



4 F. N. Schulz and R. Zsigmondy, Hofmeisters Beitriige, 3. 137 (1902). 



