THE BIOLOGICAL LITERATURE 



27 



cally by author, but many papers have more than one author, and the 

 best-known author is not always Hsted first. 



The system described in the following paragraphs is included as an 

 example only and cannot be recommended without qualification. It is 

 doubtless as expensive and difficult to keep up as any other system, but 

 it does offer the advantage of rapid retrieval of any card in the file. 



Fig. 3-1. One form of edge-punched card. 



Several firms produce edge-punched cards, of which Fig. 3-1 is an 

 example. Many sizes are available, some of which have several rows of 

 holes. The card shovm is about the size of an IBM card, for which 

 filing cabinets are easily available. The holes can be punched out, as 

 several in the illustration are, so that when a needle is passed through 

 a given hole in a stack of cards only those that are punched will fall 

 off the needle. One corner is cut off the card so that the cards in a stack 

 can be quickly sorted and placed in order, all right-side-up and facing 

 forward. Each card is prepared by copying the authors' names, the 

 tide of the paper, citation, and an abstract on the face of the card. The 

 holes in the card are then punched according to a code. 



Holes are arranged in "fields" of four, labeled 1, 2, 4, 7. By punching 

 no more than two holes it is possible to arrive at any digit from to 9, 

 as 1, 2, 2 + 1, 4, 4 + 1, etc. If two fields are used, one field can be used 

 for units, the second for tens. For example, 7 + 1 in the first field is 80, 

 4 + 2 in the second field is 6, and the two together give 86. The card 

 illustrated has 19 fields, which means that 10^^ coded bits of informa- 

 tion can be stored. This is not fully efficient because a set of four holes 

 could stand for any number from to 1 5 if the number of punches per 



