358 <v. HAROLD DREW 



were cut off by fine scissors and drawn up into the needles in this 

 way. 



In the earUer experiments portions of the ovary were injected 

 into the muscle through a hole bored in the shell. The holes were 

 drilled in the convex or right valve by an ordinary dentist's drill, 

 the head of which was prevented from penetrating too deep by a 

 lapping of thread. The spot selected for drilling was steriHsed 

 with a saturated solution of corrosive sublimate, washed off with 

 a solution of hydrogen peroxide (20 vols.) or distilled water, care 

 being taken not to allow any of the sublimate to run between the 

 valves. The transplanting needle was then introduced to the 

 required depth, slightly withdrawn and its charge projected into 

 the channel. The hole was then thoroughly dried, and stopped 

 with sealing wax. In later experiments it was found that this 

 proceeding, which occupies a good deal of time, was unnecessary, 

 and the implantation was made directly into the muscle from the 

 side. By this method there is a slightly greater risk of sepsis 

 and the consequent death of the animal, but this is more than com- 

 pensated for by the saving of time which it entails, and this is of 

 importance when a large number of experiments have to be made. 

 In some cases much larger pieces of the ovary were implanted 

 by simply making a longitudinal slit in the muscle with a small 

 scalp^, and inserting the ovarian tissue with fine pointed forceps. 

 The wound thus made is closed by the contraction of the muscle, 

 but the risk of sepsis when this method is employed is considerable, 

 and only a small proportion of the animals survived the experi- 

 ment long. 



During the experiments the animals were kept in the laboratory 

 tanks, or in basins with a continuous flow of water. Exposure 

 to too strong a fight should be avoided, and if the animals are 

 required to live long it seems to be of advantage to cover the basins 

 with green glass, or to moderate the light in some other way. 



When required for examination, the animals were killed by wedg- 

 ing the valves of the shell apart with a cork, and then placing in 

 dilute spirit. When dead, one valve of the shell was removed, 

 and the adductor muscle carefully sliced with a razor until the 

 orange color of the implanted ovarian tissue could be seen shining 



