332 COLLECTED STUDIES IN IMMUNITY. 



is highly toxic for the animal injected. If, for example, a rabbit is 

 injected intravenously with 10 cc. of dog blood whose serum has 

 not previously been removed, the animal will die acutely. By pre- 

 viously heating the serum one also obviates the reactive production 

 of serum coagulins and anticomplements, both of which can at times 

 hinder the estimation of haemolysis. A general rule as to which 

 mode of injection is to be chosen for immunization cannot be laid 

 down. Larger laboratory animals are usually injected subcutaneously ; 

 goats usually bear intraperitoneal injections very well. This mode 

 of injection, using blood-cells which have previously been dissolved 

 with water, is used especially when a particularly marked " ictus 

 jmmunisatorius " is desired, as, for example, in the production of 

 isolysins. Birds are injected into the large pectoral muscles or 

 intraperitoneally. For rabbits and guinea-pigs the intraperitoneal 

 injections are well adapted, since, if the material is not positively 

 sterile, secondary injections (which in subcutaneous inoculations 

 often lead to troublesome abscesses, especially in the rabbit) are 

 most readily avoided. Injuries to the intestine are best avoided by 

 holding the animals almost vertically, head down, and thrusting 

 the needle into the abdomen in the median line a little above the 

 bladder. The needle should not be too sharp, nor thrust in very 

 deeply. (Personal communication of Dr. R. Krause.) The repetition 

 of intravenous injections offer especial difficulties, for after hsemolysin 

 formation has once occurred the blood-cells introduced are rapidly 

 dissolved, leading to the death of the animal from embolism. 

 (Rehns. 1 ) 



Another thing which may lead to death from embolism is the 

 formation of coagulins in consequence of a previous injection of 

 blood which has not been freed from serum. These coagulins cause 

 a rapid formation of precipitates within the blood circulation. 2 



The amount of blood used depends upon the size of the animal 

 to be injected and upon the special conditions of the experiment. 

 Up to a liter of blood, freed from most of its serum, can be injected 



1 Rehns, Comp. rend, de la Soc. de Biol. 1901, No. 12; see also similar 

 observations made on man by Bier, Munch, med. Wochensch. 1901, No. 15. 



'Very likely the inexplicable results obtained by Magendie ("Vor- 

 lesungen iiber das Blut," German translation by Kriipp, Leipzig, 1839) were due 

 to the formation of coagulins. Magendie found that rabbits which had tolerated 

 two intravenous injections of egg albumin without any injury whatever immedi- 

 ately succumbed to a further injection made after a number of days. 



