SUSCEPTIBILITY TO TRANSPLANTABLE TUMORS 83 



ovary. A small incision about one-eighth of an inch is made by 

 means of curved scissors through the body wall. The edge of 

 the incision is held by one pair of forceps while a second pair 

 is inserted into the opening. With a httle practice the ovary 

 together with the oviduct can be pulled out through the incision 

 on the first trial. The ovary is now separated from the coiled 

 oviduct. The tubes and adipose tissue are replaced and the 

 inner incision sutured. The skin can then be pulled over to 

 the other side until the outer incision is in a direct line with the 

 outer surface of the other hind leg. The operation is then 

 repeated on the left side. A little difficulty is first encountered 

 by the proximity of the spleen. This difficulty can be eliminated 

 by making the inner incision slightly more caudad than the 

 corresponding one on the right side. The outer incision is 

 pulled back into its original position before being sutured. The 

 single outer incision is of advantage because about one-half 

 minute of operating time is saved and because there is not a 

 direct opening from the outside to the inside, which reduces 

 the chances of infection. 



These methods of gonadectomy are applicable to very young 

 mice as well as to adult ones. When young mice are used they 

 should be placed more completely under the influence of ether. 

 Unless this is done, the viscera may be extruded by muscular 

 contraction. If this happens, there is no use trying to save 

 the mouse. Young females are best placed for operating on a 

 warm convex surface. Care should be employed not to press 

 too tightly on the legs. Paralysis of the hind legs is frequently 

 the result. Every trace of blood must be carefully removed. 

 Diluted collodion is probably the best suturing material that 

 can be used. Just enough of the flexible collodion is placed on 

 the skin to hold the two sides of the incision in place. The 

 skin is too soft to permit the use ol suturing silk. The young 

 mouse should be held in the palm of the hand several minutes 

 until completely out of the ether. It can then be replaced 

 into the nest. The mother should be removed from the box 

 for an hour to permit the young to reacquire the odor of the 

 nest. If these precautions are employed the mortality can be 

 kept at a minimum. 



