94 CHANGES IN THE EGG. 



incubation. This supplies the place of thw 

 lungs, and carries on the respiratory process 

 instead. The lungs themselves, indeed, be- 

 gin to be formed on the fifth day, but, of 

 course, cannot perform their function while 



contained embryo. To satisfy himself on this point, he repeated 

 tbe experiment in question, in the following manner. 



Having selected a number of fresh eggs, as nearly of the same 

 size and form as possible, he varnished them over several times 

 with albumen which had been allowed to stand ibr some time 

 in an open vessel, until, by evaporation, it had acquired con- 

 siderable consistence ; this was repeated until the shells appeared 

 completely lackered. Then, with a pencil, he marked one of 

 them into equal sections like the divisions in an orange, and cut 

 a piece of card to correspond exactly with one of these divisions ; 

 then a great number of papers similar to this card ; and macer- 

 ated them for two days in albumen, until they were thoroughly 

 saturated, and so soft and pulpy that they could be readily ap- 

 plied to the egg, and the edges brought so well together, that 

 the joining was scarcely observable. Having covered the eggs 

 in this way and allowed them to dry, he repeated the papering 

 and varnishing four times, taking care to bring the middle of each 

 section opposite the joining in the previous coating. They were 

 now covered with four thicknesses of paper, besides numerous 

 coatings of albumen, first on the shell, and subsequently between 

 each layer of paper, the whole forming a covering so thick and 

 horny, that Mr. Town was convinced that it was entirely im- 

 permeable. 



The eggs thus prepared were hatched in the usual manner; 

 and to render the experiment doubly sure, they were repeated 

 with success, although he employed several coatings of oil paint 

 purposely prepared with the most noxious materials, as a test of 

 the air-proof nature of the protection used in the first instance. 



