122 - J. THOS. PATTERSON. 



B. Methods. 



For opening and sealing the egg I have in the main employed 

 the method first used by Miss Peebles ('98). By the aid of a fine 

 file a small window is made in the shell just above the blasto- 

 derm. The operation is then performed and the opening closed 

 with a slightly larger piece of shell (with membrane still attached) 

 from the corresponding part of a fresh egg. 



Although I have used very fine glass pins in some of the work, 

 yet I have found the electric needle by far the better means for 

 making the injury. These needles (No. 12 sewing needles, 

 ground as fine as possible on a water stone) were connected with 

 two dry battery cells. 1 Then, by the aid of a binocular, using a 

 combination of lenses giving a magnification of I 2.6 diameters, 

 one needle is placed at the desired point and the other is touched 

 to the albumen for a second or two. The opening is then closed 

 in the manner stated above. The whole procedure from the 

 opening to the closing of the egg need not take over a minute. 



If no further precautions were necessary the experimental 

 work would be a simple process, but the difficulties that attend 

 experimental studies on the bird's egg are many. Perhaps there 

 is none so perplexing as that of preventing infection. Previous 

 workers have realized this fact. Some writers have reported a 

 loss of embryos, due to mould or bacteria, reaching as high as 

 , 80 per cent. 



The mere heating of the instruments is not sufficient in itself 

 to prevent infection. However, I find that if one uses a .1 per 

 cent, solution of bichloride of mercury previous to heating, this 

 difficulty is practically overcome. The table upon which the 

 operation is performed, the hands, the instruments, in fact, every 

 thing connected with the operation must be thoroughly washed 

 in this solution. With a cloth moistened in the sublimate I also 

 wipe off the shell where the window is to be made, otherwise 

 small fragments of the shell falling upon the albumen will be a 

 frequent source of infection. 



1 The Cleveland Dry Battery Cells were used. Each cell has a pressure of about 

 1.3 volts. 



2 All the drawings with which this paper is illustrated were made by the aid of the 

 Abbe camera. 



