PHYSICO-CHEMICAL PROPERTIES 77 



per cent NaCl solution. Roth the dissohed precipitate and the 

 filtrate ^vere dialyzed inider toluol in parchment hags aoainst 

 running Avater initil there was no amnioniimi sidphate detected 

 inside of the bags. This usually took about forty-eight horns. 



The dialyzed solution of the precipitate was dried at 37.5° c. 

 in a Freas vactumi o\'en connected to Cenco Hyxac Pinnp. The 

 dried precipitate was ground into a fine po^vder and preserved in a 

 desiccator over ])hosphorus pentoxide at room temperattne. just 

 before use a weighed amotnit of the po^vder \vas dissolved in 

 distilled ^vater. The powder never w^ent into perfect solution; 

 however, if care was taken to add the distilled w^ater drop by drop 

 and to mix it thoroughly with the water by means of a glass rod, 

 the suspension was uniform and quite fine. 



The precipitate-free supernatant fluid was removed from the 

 bags immediately after complete disappearance of ammoniimi sul- 

 phate. The fluid was filtered and NaCl was added to the filtrate 

 to the extent of 0.9 per cent; the filtrates were then stored inider 

 tohiol in the refrigerator. In most instances the experiments were 

 made shortly after the preparation ^\as completed. 



The abo\e materials Avere tested in rabbits by the method of 

 reciprocal titration (Method I) . It became obvious from these 

 experiments that the active principles of the phenomenon could 

 be completely precipitated by saturation with ammonitmi sid- 

 phate, the supernatant fluids showing no potency whatsoever. A 

 yield of 9.1 gms. of dry po^vder ^vas obtained from 4000 c.c. of the 

 "agar ^vashings" filtrates after precipitation and dialysis. When 

 both the skin and intravenous injections of the precipitate Avere 

 made into the same rabbits, 0.1 mgm. was sufficient to prepare the 

 skin of some rabbits which sid^sequently received (per kilo) 8 

 mgms. of the precipitate intravenously. W^hen, however, the in- 

 travenous dose Avas reduced to 2 mgms. of precipitate per kilo, it 

 was necessary to use 1 mgm. intradermally in order to prepare for 

 the reaction. 



Doses of the precipitates larger than 2 mgms. per kilo injected 

 intravenously often exhibited general toxicity. The potency of 

 the precipitate preserved over phosphorus pentoxide in a desic- 

 cator at room temperattne, remained unchanged for seven months 

 after its preparation Avas completed. 



The method of reciprocal titrations employed in these experi- 

 ments makes difficidt the accinate estimation of the percentage 



