Individual Differences 159 



for the same animal would appear to show but a very slight difference, 

 if any. We see that lactosera and haematosera both act similarly. 

 Although there may be quantitative differences there are none 

 apparently of a qualitative character. Comparative quantitative ex- 

 periments have still to be made. 



As in haematosera, the precipitin contained in lactosera is very 

 stable. Moro (31, X. 1901) found it still gave reactions with its 

 homologous milk after being sealed for months in capillaries, thus 

 confirming what I have found for some haematosera. Lactosera with- 

 stand a temperature of 56 C., in this resembling the haematosera, 

 and the agglutinins. On warming lactoprecipitum in normal saline 

 it almost completely redissolves. Moro obtained lactosera by treating 

 animals with pure powdered human or cow's casein. 



Milks of the same species show individual differences according to 

 Moro (loc. cit.\ in their reaction to lactosera. On the other hand, the 

 reaction of each individual milk to lactoserum, as tested on the milk of 

 wet-nurses, remained constant. Individual differences were less marked 

 in cow's milk. The individual difference was shown by the reaction of 

 each milk to its homologous antiserum taking place with higher dilutions 

 than with a non-homologous antiserum. Personally I am inclined to be 

 somewhat sceptical on this point in consequence of the results which 

 I have obtained with Mr Strangeways with haematosera. To prove 

 the presence of individual differences, and I do not question but that 

 there may be such, it is necessary to examine a large series of antisera 

 and homologous milks or sera, and this does not seem to have been 

 done by Moro. His results have therefore to be accepted with caution. 

 I will however state the reasons which led him to the conclusion that 

 there are individual as well as specific groups in a given milk. 



1. Antiserum for milk A added to milk a gives reaction in a high dilution, 



and vica varsd. 



2. Antiserum for milk A added to milk b gives no reaction in a high dilution, 



and vice vend. 



The reaction is due in the first instance to the specific and individual 

 groups entering into combination. In the second instance, using a 

 stronger dilution, only the specific, not the individual groups combine. 

 The deficit in the reaction A plus b, cannot be made good by adding 

 more of milk b. He concludes, therefore, that the specific groups are 

 neutralized, or destroyed, only the individual ones which are least 

 numerous being left. These being unable to combine account for 



