52 



FIELD ORNITHOLOGY. 



the drill perpendicularly Xo the surface, unless it be preferred to prick with a needle first. 

 A twirling motion of the instrument gradually enlarges the opening by filing away the shell, 

 and so bores a smooth-edged circular hole. This should be no larger than is required to 

 insert the blow-pipe loosely, with room for the contents to escape around it. Nor is it always 

 necessary to insert the pipe ; a fine stream of water may be easily injected by holding the 

 instrument close to the egg, but not quite touching. The blowing should be continuous and 

 equable, rather than forcible ; a strong puff easily bursts a delicate egg. Be sure that all the 

 contents are removed; then rinse the interior thorouglily with clean water, either by taking a 

 mouthful and sending it through a blow-pipe, or witli the syringe. Blowing eggs is a rather 



fatiguing process, more so 



than it might seem ; the 



cheek muscles soon tire, 



and the operator actually 



becomes ''blown" himself 



before long. The opera- 

 tion had better be done 



over a basin of water, both 



to receive the contents, and 



to catch the egg if it slip 



from the fingers. The 



membrane lining the shell 



should be removed if pos- 

 sible. It may be seized by 



the edge around the hole, 



with the forceps, and 



drawn out, or picked out 



with a bent pin. But this 



is scarcely to be accom- 

 plished in the case of fresh 



eggs, when the membrane 



may be simply pared 



smoothly around the edge 

 of the hole. Eggs that have been incubated of course offer difii- 

 culty, in proportion to the size of the embryo. The hole may be 

 drilled, as before, but it must be larger ; and as the drill is apt to 

 split a shell after it has bored beyond a certain size of hole, it is often 

 well to prick, with a fine needle, a circular series of minute holes 

 almost touching, and then remove the enclosed circle of shell. This 

 must be very carefully done, or the needle will indent or crack the 

 sheU, which, it must be remembered, grows more brittle towards 

 the time of hatching. Well-formed embryos cannot be got bodily through any hole that can 

 be made in an egg ; they must be extracted piecemeal. They may be cut to pieces with the 

 slender scissors introduced through the hole, and the fragments be picked out with the 

 forceps, hooked out, or blown out. No embryo should be forced through a hole too small ; 

 there is every probability that the shell will burst at the critical moment. Addled eggs, the 

 contents of which are thickened or hardened, offer some diificulty, to overcome which persistent 

 syringing and repeated rinsing are required ; or it may be necessary to fiU them with water, 

 and set them aAvay for such length of time that the contents dissolve by maceration ; carbonate 

 of soda is said to hasten the solution ; the process may be reiieated as often as may be necessary. 

 In no event must any of the animal contents be suffered to remain in the shell. When emptied 



Fig. 6. — Scissors, knives, and 

 e; after Newton. 



, J nat. 



Fig. 7. —Hooks for ex- 

 tracting embryos, nat. size ; 

 after Newton, a, 6, c, plain 

 hooks ; d, bill-hook, having 

 cutting edge along the con- 

 cavity. 



