144 The Microscope. 



ELEMENTARY DEPARTMENT. 



RUDIMENTS OF PRACTICAL EMBRYOLOGY.* 



W. p. MANTON. 



SECTION III. 



PREPARATION OF THE EMBYRO. 



§ 6. The egg jhaving undergone the required amount of 

 incubation is removed from the incubator or nest, the marked sur- 

 face always remaining uppermost (for the reason that the embryo 

 lies on top of the yolk), and rested on a glass individual salt- cellar. 

 A sharp rap is then given the larger end of the egg, so that the 

 shell is broken, and air let in. The egg and cellar are then trans- 

 ferred to a dish of the salt solution which has been warmed to blood 

 heat. The depth of the salt water should be sufficient to quite 

 cover the entire egg. The upper part of the shell must now be 

 broken by a few taps of the scalpel or scissors, and the pieces 

 removed with fine forceps, over a space the size of a quarter dollar, 

 or larger, according to the period of incubation. 



This requires some little attention, as the sharp bits of shell are 

 apt to turn inward and cut the embryo or open the yolk. When the 

 shell has been taken away, the embryo will be seen lying within two 

 rings (area opaca, area pellucida), or in the midst of a vascular 

 spot varying in size according to the time that incubation has pro- 

 gressed. A circulating cut must now be made around these rings, 

 with a pair of fine-pointed curved scissors — those used by oculists 

 are the best — and the disk containing the embryo floated off and 

 washed free from all adhering yolk, by gently agitating it with the 

 forceps in the salt solution. 



HARDENING. 



§ 7. Previous to opening the egg a small glass dish — a sauce 

 dish will do — should be prepared with a layer of wax, about a 

 quarter of an inch deep, at the bottom. This is quickly done by 

 pom'ing melted beeswax of the shops into the dish, and allowing it 

 to spread out evenly. The dish is then partially filled with the 



♦Copyrighted. 



tXhe egg of the domestic fowl is taken for illustrating the technique, and whatever is 

 said applies to that; the eggs of all other species may be treated in essentially the same 

 manner, varying slightly in detail. Thus a holoblastic embryo, i. e., an embryo from an 

 egg which undergoes total segmentation,— (mammalian ovum) cannot be pinned out, as can 

 a viero-blastic embryo, i. e., an embryo from an egg which undergoes only partial seg- 

 mentation (avarian ovum). 



