530 



APPENDIX 



Cage Tags. — There are two main types of cage tags, those which provide only a 

 location number on a rack and those which provide not only the location but additional 

 information such as the numbers of the animals in the pen, their birth and mating dates, 

 strain and generation. On such tags pregnancy and litters are also recorded. In 

 some genetic experiments it has been possible and efficient to use the cage tags in place 

 of the pedigree card. When this is done, the ledger number is placed on the cage tag 

 beside the record of the birth of the litter (figures 75 and 76). 



Card File. — A card-file box is the usual repository for the pedigree cards. Several 

 systems can be used. 



1 . If all the cards in one box pertain only to one strain, so indicated on the front, 

 then it is not necessary to use any file-guide cards but merely file the pedigree cards 

 according to date of birth (putting youngest in front) or according to cage number. 

 The efficiency of the birth-date system is particularly noticeable in a large colony when 

 a large number of pairs must be replaced at regular intervals. Example: It is usual 

 in the pedigreed expansion stocks to replace breeding pairs at a stated interval which 

 varies with the strain in use. The number to be made up varies slightly from month 

 to month so that the number of boxes (2 pens per box) will equal a section. In 

 C57BL/6J the replacement has been determined as 7 months. Therefore in September 

 1963 all pairs mated in February 1963 will be removed from the colony and replaced 

 by the desired number of new pairs. These in turn will be replaced in 7 months 

 (March 1964) by other new pairs. When the card file is arranged according to date of 

 birth it is easy to see which animals should be removed in September (all those born 

 in January, which were mated in February) . 



Fig. 75. Cage tags. 



bSAT -13> 



Left. Cage tags may show only the strain and number of the pen. Right. If the cage is 

 not a breeding cage some other notation may be used. Many times, only numbers appear 

 on such tags. 



