94 



Scientific Proceedings (38). 



S 8 (468) 



A note on the parabiosis of rats and mice. 1 

 By R. A. LAMBERT. (By invitation.) 



[From the Pathological Department of the College of Physicians and 



Si(rgeons.~\ 



This study includes 50 parabioses between rats and mice, 

 twenty of which were terminated before the fifth day by the death 

 of one of the animals, usually the mouse. That is, only thirty 

 lived sufficiently long to admit of a union, or to determine if a 

 union would take place. Of this number twelve showed a more 

 or less complete tissue connection. One pair lived twenty-eight 

 days, but the majority died between the seventh and fourteenth 

 days. This compares favorably with the mortality observed where 

 mice alone were used. 



The technique employed consisted in a peritoneal anastomosis 

 from 2 cm. to 3 cm. long, and a skin muscle apposition for about 

 double this distance. Young rats weighing about forty grams 

 were used, with " growing " mice from a large breed. Additional 

 sutures through the skin of the shoulder and neck and adhesive 

 plasters about the body gave sufficient fixation. 



The existence of a true anatomical union is based on : (1) 

 histological studies ; (2) recovery in a second animal of substances 

 injected into the first ; (3) hemorrhage from one animal through 

 the dead tissues of the other (noted twice). 



The healing process is not essentially different from that taking 

 place in the individual animal, except that in some instances the 

 inflammatory reaction is more marked and the development into 

 scar tissue slower. The skin unites with much less frequency than 

 the deeper tissues — five cases out of twelve in this series. In many 

 animals which fail to unite there is an absence of suppuration and 

 the line of demarcation between the two tissues is indicated by an 

 indefinite narrow zone of necrosis. 



Seven parabioses between rats were made for comparative 

 study. In one of these pair of three weeks duration, after death 

 of one of the animals, incision was made in the dead rat nearly a 

 centimeter from the line of union. A definite capillary oozing 

 resulted. An injection of India ink was made immediately through 



1 This investigation has been done under the George Croker Special Research Fund. 



