454 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



The cells which are separated in the neighbourhood of the 

 ovum I consider as a secretion of the third order. They have 

 passed off from the uterine glands entire, and possess a power 

 peculiar to the third order of secretions, the power of under- 

 going further development after being detached from the ger- 

 minal spots or membrane of the secreting organ. 



Prom what has now been stated, it appears that the 

 decidua consists of two distinct elements ; the mucous mem- 

 brane of the uterus thickened by a peculiar development, and 

 of a non-vascular cellular substance, the product of the uterine 

 follicles. The former constitutes at a later period the greater 

 part of the decidua vera, the latter, the decidua reflexa. This 

 view of the constitution of the decidua, clears up the doubts 

 which were entertained regarding the arrangement of these 

 membranes at the os uteri, and entrances of the Fallopian 

 tubes. It is evident that these orifices will be open or closed, 

 just as the cellular secretion is more or less plentiful, or in a 

 state of more or less vigorous development. It also removes 

 the difficulty of explaining how the decidua covers the ovum, 

 a difficulty which cannot be reconciled with the views of Dr. 

 Sharpey, who is obliged to suppose the deposition of lymph, 

 which is only the old view of the constitution of the decidua. 



When the ovum enters the cavity of the uterus, the cellu- 

 lar decidua surrounds it, and becomes what has been named 

 the decidua reflexa, by a continuation of the same action by 

 which it had been increasing in quantity before the arrival of 

 the ovum. The cellular decidua grows around the ovum by 

 the formation of new cells, the product of those in whose 

 vicinity the ovum happens to be situated. 



At this stage of its growth, the ovum with its external 

 membrane, the chorion, covered by tufts, the structure and 

 functions of which have been described in the second part of 

 this Memoir, is imbedded in a substance which consists 

 entirely of active nucleated cells. The absorbing cells of the 



