ANTIBODIES II 23 



particular, often failed to avail themselves as fully as they might 

 have of statistical methods (Batson, 1951). The situation has 

 pretty well been corrected in recent years, however. A summary of 

 some of the current applications of statistics to immunology will 

 be found in my Fundamentals of Immunology (Boyd, 1956). Indeed, 

 it is to be feared that today there are a few biologists who feel, 

 as many physical anthropologists did 30 years ago, that statistics 

 will cure all ills. Actually, of course, the results of statistical analysis 

 can never be better than the data themselves. A false sense of security 

 stemming from a blind application of statistical methods to situations 

 where they are not appropriate can be as bad as the former tendency 

 to avoid their use. 



Stereoisomerism 

 Having shown that antibodies can distinguish structural isomers, 

 Landsteiner naturally asked if they could also distinguish stereoiso- 

 mers and therefore next turned his attention to this problem. In 

 organic chemistry it is established that, whenever a carbon atom has 

 four different groups attached to it, there are two possible arrange- 

 ments of these groups which are essentially different from each other, 

 somewhat as the right and left hands differ from each other (Fig. 2-7). 



X 



z z 



Fig. 2-7. Models of right- and left-handed molecules. 



The essential difference between the two possible isomers in such 

 a case is correctly shown only in three dimensions. Since it is not 

 generally convenient to have three-dimensional models in front of 

 us when discussing isomerism, it is customary to represent such com- 

 pounds by a projection on two dimensions, as shown below. 



X X 



I I 



W - C - Y Y - C - W 



I I 



z z 



