62 The Precipitim: Methods 



claims to have obtained antisera from eels treated with rabbit serum, 

 and Hamburger obtained effective antisera for rabbit blood by treating 

 goats therewith. Wassermann and Schtitze have apparently also failed 

 to obtain antihuman serum from the goat. 



Judging from the blood reactions obtained, I am inclined to the 

 theory that an antirodent serum will act upon the rodent group, as I 

 have found with other antisera in other groups. The rodents form such 

 a well-defined order among the mammalia that it appears theoretically 

 probable that they will produce antisera for practically any animal 

 outside a rodent. The rabbit is therefore the animal par excellence for 

 the purposes of such experiments. 



Collecting Bloods and testing them with Antisera. 



The bloods or sera tested wore collected in two ways, viz. fluid and dry. 

 The fluid sera were relatively few in number because of the practical 

 difficulty of obtaining sera in this way. The fluid sera were obtained 

 by collecting blood in covered vessels where it was allowed to clot, the 

 serum being subsequently removed to clean or sterilized well-stoppered 

 bottles and a small amount of chloroform added for purposes of preser- 

 vation. Dilutions of fluid sera were made in salt-solution, the dilutions 

 being usually of 1 : 100 or thereabouts. A number of fluid sera were filtered 

 through sterilised Chamber-land and Bcrkefeld filters and subsequently 

 preserved in sealed tubes. In other cases the dilutions were preserved 

 by the addition of small quantities of chloroform, and it was found that 

 such dilutions gave good reactions after over a year, the bottles having 

 been kept at room temperature in the dark. Although long-stored 

 bloods usually give somewhat less reaction than do fresh ones, the 

 reverse may be the case. It is a remarkable fact, which will be 

 brought out more clearly in describing the results of the quanti- 

 tative tests, that sera or serum-dilutions preserved for six months 

 or more will at times give more precipitum on the addition of an 

 anti-serum than do the fresh sera. This applies not only to the amount 

 of precipitum obtained by the addition of an homologous anti-serum to 

 a serum dilution, but also to what I have termed the " mammalian 

 reaction," namely one taking place between a powerful non-homologous 

 antiserum and a more distantly related blood. Whereas this increased 

 amount of precipitation obtained with older sera (the increase may 

 amount to 50 / ) will naturally greatly affect the quantitative tests, it 

 can be practically ignored in the qualitative tests here described. On 

 what this change in stored blood depends is a matter for future 



