EFFECTS OF GONAD GRAFTS IN CHICKS O 



cent alcohol with or without iodine. A small piece of shell, 

 generally 10 to 15 mm. square was then cut out from the sterilized 

 surface, leaving the egg membranes intact. Then a V- or U- 

 shaped sht was made through the shell membranes by means of 

 the very sharp point of an insect pin, sterilized in the flame. 

 The cut edge of the membranes was lifted up and a piece or some- 

 times pieces of the organ to be grafted placed on a desirable 

 spot on the surface of the chorio-allantoic membrane by means 

 of the pin point. It is probable that in this operation the chorio- 

 allantoic membrane was injured to some extent in the majority 

 of cases. It was observed that the most favorable place for 

 inserting the grafts is at the junction of blood-vessels on the 

 chorio-allantoic membrane. As quickly as possible after placing 

 the graft, the slit in the egg membranes was closed, and the piece 

 of shell which had been removed replaced and sealed with paraffin. 

 Sometimes a piece of paper previously immersed in melted paraf- 

 fin was used to close the opening with equally good results. The 

 operated egg was then returned to the incubator for further 

 development. 



Previous to such an operation it was of course necessary to 

 prepare the organ which was to be grafted. Organs were re- 

 moved from a chick and cut into small pieces about 1 mm. 

 square. These pieces w^ere kept moist in a Petri dish until the 

 egg had been prepared for receiving them. 



All of the instruments employed in the operation were sterilized 

 in the autoclave. 



The grafted organs were generally gonads. However, other 

 organs, such as thymus, thyroid, spleen, fiver, kidney, and others, 

 were also grafted upon developing eggs in order to compare their 

 effects upon the embryos with the effects produced by the gonads. 



In each experiment generally ten to thhty eggs were operated 

 upon and grafts from a gonad placed upon their chorio-allantoic 

 membranes. A few control eggs were incubated simultaneously 

 with each such lot. Some of these control eggs were treated in 

 the same way as the operated eggs, a piece of paper or paraffin 

 or shell being placed upon the membrane instead of a piece of 

 organ; in other cases a window was made and closed without 



