398 



Dr. H. G. Chapman. On the Weight of [Apr. 21, 



currents supplied to the electric furnaces. This may have been in reality a 

 subjective phenomenon similar to that now recorded. 



No effect upon the senses of smell, taste, or hearing has yet been observed. 



[Added April 14. — Since the above was written, it has been noted by 

 several observers that a sensation of taste in the mouth is excited after 

 exposing the head for two or three minutes to the action of the alternating 

 magnetic field.] 



On the Weight of Precipitate Obtainable in Precipitin Interactions. 



By Dr. H. G. Chapman. 



(Communicated by Dr. C. J. Martin, F.R.S. Received April 21, — Eead 



May 5, 1910.) 



(From the Physiological Laboratory of the University of Sydney.) 



The nature of the interaction between the antiserum and homologous 

 protein in a precipitin test has been the subject of several researches. It has 

 been usual to mix a given fixed quantity of antiserum with increasing 

 quantities of suitably diluted homologous protein estimated either directly or 

 in terms of dilutions and to measure the volume of the precipitate formed. 

 The experiments of Hamburger which have been analysed by Arrhenius* were 

 conducted in this way. Welsh and Chapmanf also examined mixtures of a 

 fixed quantity of antisemm with increasing quantities of homologous protein 

 by adding to the superfluid above the precipitate either antiserum or 

 homologous protein. This mode of testing the superfluid after the completion 

 of the precipitin reaction led to certain definite conclusions. In the first 

 place the further addition of antiserum to the superfluid always led to the 

 formation of a further precipitate. In the second place it was possible to 

 neutralise completely the precipitin in an antiserum, so that the further 

 addition of homologous protein led to no more formation of precipitate. 



The precipitin reaction between antigen and anti-body is very suitable for 

 quantitative study owing to the simple nature of the interaction and the ease 

 with which the quantities may be measured. More accurate methods 

 are, however, required for its study than those previously employed. The 



* S. Arrhenius, ' Ininiuno-chenilstry,' New York, 1!)07, p. 287 et seq., and 'Ergebniase 

 d. rhysiol.,' vol. 7, p. 54.3, 11)08. 



t ' Journ. of Hygiene,' vol. G, p. 251, 1906. 



