Developments of a Pfaffian. 41 



we see that to reach the six well-known terms of I a. b. c h I we 

 have to handle 1 set of 15 terms followed by 3 sets of 3 terms 

 each, the last 9 terms appearing merely for the purpose of cancelling 

 9 of the 15 which precede them ; furthermore, six variables occur 

 in the development which have nothing to do with the function 

 sought to be developed. 



