SYSTEM USED IM BREEDING GUIXEA-PIGS AND EL'VRBITS. 3O9 



in any way and if properly inserted they do not tear out. If 

 desired the tags may be used in duphcate, one in either ear. 



In our first experiment with this tag on guinea-pigs we made 

 the mistake of putting it too close to the head and bending the 

 points too far back. If these point? are pressed too firmly 

 against the skin they often cause a slight irrigation which may 

 end in suppuration. In a few cases such tags were lost in the 

 course of three or four months. However if the tag is placed 

 just outside the heavy cartilage in the ear and the points are 

 not pressed down too firmly w^e have never had any trouble of 

 this kind. The difficulty would be entirely eliminated if the 

 points of the tag were made a little longer. 



The voung guinea-pigs are so well developed at birth that they 

 can be labeled at once without causing them any inconvenience. 

 As a matter of fact, however, we find it more convenient to 

 have the attendant place the pregnant females in separate cages 

 a few days before parturition. He can then mark on the cage 

 the date of birth and the number of young. About once a week 

 we can then go through pud label the young and make the 

 necessary records. This involves but very little time and 

 trouble. In the case of rabbits it is better to let the young get 

 three or four weeks old before labeling them. 



Since the principal object in growing guinea-pigs at the Ken- 

 tucky Station was to furnish a sufficient supply for physiologi- 

 cal and bacteriological w'ork it was necessary to handle them by 

 slightly different methods than are used by the experimental 

 breeder. Alost of the breeding is done in pens rather than in 

 hutches. It has been found that better results are obtained if 

 not more than 6 or 7 females are mated with one male. The 

 pens are sub-divided by removable partitions into small areas 

 about 2x4 feet. One male is kept in each of these pens and the 

 females are placed in them, together with their young as soon 

 as these latter have been tagged. When the young are about 

 three weeks old they are removed to separate pens and the sexes 

 separated. One pen contains surplus males which may be 

 desirable for use in breeding. Two or more larger pens 4x4 

 feet), contain the surplus animals for experimental purposes. 

 The sexes are separated, except that one male is placed in each 

 pen of females so that if any females should remain long 

 enough to bear young the pedigree system will remain intact. 



