234 



Prnfcssor SvanU Arrhejiiuf^ 



[June 9, 



action takes place l)etween the precipitate already formed and the 

 fnrther addition of the antigene, whereby the precipitate becomes 

 dissolved. Hamburger has given an example of this kind. It relates 

 to serum from the horse, and immune serum, containing precipitin, 

 from the calf. The horse serum was attenuated to a fiftieth, and 1 c.c. 

 of that preparation corresponded to three times the used quantity of 

 calf's serum, namely 1 c.c, which is considered equal to 100 ; there- 

 fore, 1 c.c. of the diluted horse serum was considered equal to 800 in 

 the formula for calculation. The maximum quantity of precipitate 

 corresponded to KiO units, but in the experiments only 59 units were 

 obtained, l)ecause the dilution was rather great. The results of these 

 experiments are contained in the following table : — ■ 



Even in this case the observations agree well with the calculation. 

 It nmst, however, be remembered that we have here four constants 

 to determine experimentally, namely, the number of equivalents 

 (counted in units of precipitate) contained in 1 c.c. of each of the 

 two sera, and further two constants of equilibrium for the two com- 

 pounds, the precipitate and its soluble compound with the albuminous 

 substance in the horse serum. It is thereby possible to obtain a 

 fairly good agreement, if the errors of observation are not too 

 great. 



The immune serum from a rabbit injected with sheep's serum 

 gives a precipitate with the serum not only of sheep, but also of 

 related animals, as goats or cows. In these cases the quantity of 

 precipitate was less ; instead of 800 units per c.c. in the sheep's 

 serum, the corresponding figures were, for the goat's serum 212, and 

 for the serum of cows only 90. These figures indicate that sheep 

 and goats are very nearly related, and in a much lesser degree 

 related to cows. This method evidently gives a possibility of deter- 

 mining the relationship between different animals quantitatively. As 

 is well known it has already been used for similar determinations, 

 but only qualitatively. 



In the early days of the development of the doctrine of immunity 



