260 ON THE EGG. 



brane richly supplied with blood-vessels and nerves, and per- 

 forms a truly remarkable part in the process of egg-making. It 

 is divided, but functionally only, into three parts, continuous 

 with each other, each giving out a distinct and peculiar secre- 

 tion as the egg passes down it. The little globular ova in the 

 ovarium, which are really the seeds of the bird, enlarge, develop, 

 and ripen one after another at the rate of one, or sometimes even 

 two, in twenty -four hours during the laying season. When one 

 has become mature, it bursts the general wall of the ovary, and 

 drops into the expanded upper end of the oviduct, which receives, 

 embraces, and presses it on gently into the tube. The nerves 

 and blood-vessels of the oviduct become excited, the nervous 

 impressionability is heightened, more blood rushes into the part, 

 and the whole oviduct becomes largely swollen, reddened, and 

 prepared for action. Now, the ovum, which is the yolk of the 

 future egg, is no sooner fairly lodged in the oviduct than it is 

 flooded over by an albuminous liquid rushing out from the ex- 

 cited walls of the oviduct. This is the white of the egg, and it 

 is laid on in successive strata. The ovum thus enlarged distends 

 the oviduct. This excites contraction of its muscular wall, which 

 drives the ovum onwards to the second part of the duct. There, 

 a different secretion is poured out by the mucous membrane, and 

 which is scanty as compared with the previous one. It resolves 

 itself into minute filaments, which are interlaced in every direc- 

 tion, forming a fine fibrous membrane, which completely encloses 

 the white. A first layer being thus finished, another, exactly 

 like it, is laid over it, and the two constitute what is called the 

 membrana putaminis, or shell-membrane — a first defence of the 

 fluids within, and a platform on which the shell may be safely 

 laid down. This rougher, and quasi-foreign body, excites the 

 mucous membrane, which had produced it, to rouse the muscular 

 wall to contract and push the more than half made egg further 

 down, and into the third division of the oviduct. There the 

 excited mucous membrane gives out a third secretion, which is 

 copious, covering over the shell-membrane, and consisting almost 

 altogether of a solution of carbonate of lime. Layer after layer 

 is given forth till the supply is exhausted ; tliis being so, and 



