78 



TJw Precipitins: Methods 



Corrosive sublimate and anti-ox serum 



Copper sulphate and anti-ox serum 



Silver nitrate causes an opaque white cloud on dilution with salt 

 solution up to 1 in 10,000. Dilutions below this do not affect serum 

 when added to them. 



Formalin in 1 in 10 dilutions causes marked clouding, which 

 increases till the whole contents of the tube are opaque white. 

 Dilutions below 1 in 100 do not cause sufficient clouding to interfere 

 with the specific reaction. Solutions of thymol of 1 in 100 cause slight 

 cloudings, but lower dilutions do not apparently affect sera. 



Lysol and lysoform both cause great turbidity when added to salt 

 solution even in low dilutions, and moreover even in very low clear 

 dilutions the addition of serum causes clouding. No method has been 

 devised for getting rid of these effects ; consequently the presence of 

 these substances except in very small quantities would render the test 

 of doubtful value. 



The effects of the reagents, which for the sake of convenience we have 

 grouped under the heading of antiseptics, are very marked except in 

 the case of the volatile class. Some of the latter when added in full 

 strength to liquid sera produce heavy deposits, but the supernatant 

 fluid retains its properties. Formalin and corrosive sublimate in 

 strong solutions, as well as the sulphates of copper and iron and nitrate 

 of silver in much weaker dilutions, completely destroy the precipitum- 

 forming property. Lysol, lysoform, and similar antiseptics, owing to 

 their property of forming cloudings with salt solution, render the 

 application of the test of doubtful value in their presence." 



In order to determine quantitatively ^ the effects of the prolonged 

 action of antiseptics on fluid sera, the following experiments have been 

 carried out by Graham-Smith (29, vii. '03, p. 358). 



" Antiseptics in the proportions given below were added to fluid ox 

 and sheep sera, and allowed to act in sealed bulbs for 4 months. None 

 completely checked bacterial growth. After this period dilutions of 1 — 21 



^ For description of my quantitative method, see Section VII. 



