Tattooed Rats

Rats are not generally considered either popular or useful animals. But to scientists, who use them for biological and psychological experiments, they are both. In many laboratories, in which dozens of rats are kept in one cage, it is essential that they be marked in some way so that any one rat can quickly be singled out from all the other rats. Labels attached to the rats or marks painted on them are not entirely satisfactory. A more popular method is notching or perforating the ears according to a code. Another is cutting off various combinations of toes, or different lengths of tail. Healing and regeneration of tissue sometimes blur such labels, however, and laboratory assistants sometimes make mistakes in the code pattern.

In Science last week Psychologist Frank A. Beach Jr. of Manhattan's American Museum of Natural History announced a neat solution of this minor but often troublesome problem. The solution: tattooing. Instead of using a code, ordinary numbers are electronically tattooed in the rats' ears. In this way, Dr. Beach declared, "young rats can be marked for life at the time of weaning."

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