146 IMMUNIZATION 



it did not sink to 25 per cent until after six hours. 

 Still more startling results were obtained if the 

 rabbit had received a moderate dose of serum from 

 the common cuttlefish, Octopus vulgaris, 2-5 hours 

 before the injection of the Maja serum, which then 

 did not sink more than to about 50 per cent during two 

 days. The substance which neutralizes the Maja 

 serum must therefore be bound or hampered in its 

 action by Maja, or still more by Octopus serum, which 

 has been introduced two to three hours before the 

 investigated Maja serum was injected. 



The circumstances become still more complicated 

 when we consider that the rabbit at a later sta^e 



o 



secretes in its blood a substance, a precipitin, which 

 binds and precipitates the Maja serum. But this 

 substance does not occur in a sensible degree during 

 the first hours after the injection there is a consider- 

 able time of incubation. VON DUNGERX connects 

 the rapid disappearance of the Maja serum from the 

 blood-vessels of the rabbit with its power of secreting 

 the specific precipitin against the Maja serum. If 

 we inject Maja serum into the veins of the cuttlefish 

 Eledone moschata, or into the so-called sea-rabbit, 

 Aplysia depilans, which do not prepare any precipitin 

 or otherantibody against Maja serum in their veins, we 

 are able to demonstrate the presence of Maja serum in 

 the blood of these animals some weeks after the injec- 

 tion by mixing the blood-serum with precipitin against 

 Maja serum from rabbits. If we inject Maja serum 

 into a rabbit which has had sufficient time to secrete 

 a moderate quantity of the precipitin specific to its 



