Animal Morphology. 87 



It may be well to remember that in its analogue in 

 oviparous animals and birds, the oviducts, x by a process 

 of secretion, obtain for the ovum the material for its outer 

 shell; which, when completed, and imbibition can no longer 

 go on, though the function is retained for the use of the 

 following immature ovum, the active secreting surface 

 refuses to retain in situ the living mass, which needs no 

 further lime to form an external casement. The excess 

 of that material, not being freely appropriated by imbibition, 

 will act as a stimulant to bring into play nerve and 

 muscular power. 



That such is the case in the human being is inferred 

 from a variety of incidents which have presented them- 

 selves in actual practice, but the enumeration and circum- 

 stances of which would trench too much upon space in so 

 short an abstract as is the present ; but one thing can be 

 referred to without requiring much detail. It is the fre- 

 quency with which calcareous matter is found infiltrating, 

 sometimes slightly, and sometimes very much, into the 

 substance of the placenta and the mucous surface of the 

 uterus opposite to the placenta. 



Occasionally it is so abundant as to convert the placenta 

 into a semi-bony substance of considerable hardness and 

 roughness, and, in detaching it from the uterus, requires 

 very considerable nerve as well as manual dexterity. The 

 great danger, of course, in such cases, is the violent stream- 

 ing haemorrhage. 



Having said so much about the genito-urinary mem- 

 brane, the next membrane to be considered is the Mammary 

 membrane, which, in its transpositions, displacements, and 

 differentiations, is as singular as any membrane hitherto 

 considered. 



The mammae are singular organs, as bags and teats in 

 cattle, swine, dogs, etc., etc. Though variable in their forms 



