124 



The Nature of Precipifiu Beactions 



strength to some extent, though differences exist in the rate at which 

 this occurs. 



Antidiphtherial horse serum four years and six months old preserved 

 with trikresol was found to produce a good but somewhat flocculent 

 specific precipitum amounting to "0572 c.c. 



In the above experiments anti-human serum No. I. was only a few 

 days old, whereas No. II. was three and a half months old, and was 

 moreover contaminated by bacterial growths. The first anti-fowl's egg 

 serum was quite fresh and the second three months old. 



All sera of the same kind do not give with the same antiserum 

 identical precipita, nor even the sera of the same individual at different 

 times in some cases, consequently an accurate determination of the 

 influence of age is not possible. Our experiments however seem to 

 point to a slight decrease in strength as the result of age, the human 

 serum and fowl's albumin experiments showing a decrease of 

 precipitum of 7 7o and 12 "/o after 9 and 14 months respectively. The 

 fowl's albumin kept for 9 months shows a decrease of 33 7o- It is, 

 however, by no means easy to get accurate dilutions of egg albumin, 

 and the relative weakness of the specimen may be due to this cause. 



The two experiments just quoted also indicate that antisera lose 

 some of their power, but not to the extent that some observers have 

 stated. Some undoubtedly preserve their power of producing specific 

 reactions after the lapse of 12 months. Others lose this property more 

 rapidly, whilst some, as Nuttall has also found, become untrustworthy 

 after a time, giving cloudings with all sera. 



In considering the general results of these tables it appears that in 

 the case of dried bloods time pei^ se does not destroy their capacity 



