70 



J. Thos. Patterson. 



of the embryo and that of the chalazse, and consequently enables 

 one to decide whether or not it is necessary to discard the egg. 



For making the injury a No. 16 ''bead" needle is employed. 

 Although the diameter of this needle is small, yet it is entirely 

 too large for very fine work, and so it was ground down to the 

 desired diameter on an emery stone and then polished on a fine 

 water-stone. By this means I have been able to secure a needle-point 

 with a fineness of about 0.04 mm. 



Fig. II. Apparatus used in operating. 



By the aid of a special piece of apparatus, which is, in part, a 

 modification of the one described by McClendou ('06), the needle 

 is inserted in the blastoderm at the desired point. This apparatus 

 is attached to a binocular and consists of an upright post fastened 

 to the left end of the sliding bar of a Spencer mechanical-stage. 

 Within the post the vertical end of an elbow is moved up and down 

 by means of a rack and pinion. On the free end of the horizontal 

 part of the elbow is a clamp which works on a universal joint. In 

 operating, the needle-holder, which is connected with two dry battery 



