Generation and Development. 385 



it eventually forms the amniotic portion of the cord. The 

 liquor amnii i« an albuminous alkaline fluid, yellowish in 

 the early period of gestation, reddish toward the end of it, 

 probably due to discoloration with meconium. It consists 

 of albumin, mucin, globulin, sugar, urea, lactic acid, keratin, 

 calcium sulphate, phosphates, and sodic chloride ; it con- 

 tains also portions of hoof, epithelium, etc. 



Gurlt, quoted by Fleming, puts it at 2 lbs. 12 ozs. at the 

 twenty-first week of pregnancy in a mare, and at the 

 fortieth week the amniotic and allantoic fluids amounted to 

 19 lbs. The function of this fluid is protective to mother 

 and foetus, and during parturition it dilates the os and 

 lubricates the passage. 



The Allantois is formed from the splanchnopleure, grow- 

 ing out from the body of the embryo at the future um- 

 bilicus. As it grows from the umbilicus it spreads out, and 

 in the mare completely envelops the amnion, though in 

 ruminants it only partially envelops it. The part of the 

 allantois within the body of the embryo becomes the bladder, 

 and this is brought into communication with the allantois 

 outside the body, by means of the urachus, which passes 

 through the umbilicus ; the urine from the bladder passing 

 through the urachus, distends the allantoic sac with this 

 fluid. The outgrowth of the allantois is to establish com- 

 munication with the vascular covering of the embryo, the 

 chorion ; in the mare it lines the chorion as well as being 

 reflected over the amnion. 



The allantoic fluid of the mare is at first colourless or 

 turbid, but later becomes brown ; it contains albumin, 

 sugar, urea, lactic acid, phosphate of lime, soda, and 

 magnesia, and in the cow allantoic acid. 



Floating in the allantoic fluid of the mare are certain 

 peculiar bodies of a brownish colour, termed hippomanes ; 

 they contain much oxalate of lime. Some of these bodies 

 are attached to the wall of the allantoic sac. Their use is 

 unknown. 



In ruminants the allantois is smaller, and only partially 

 envelops the amnion ; it is attached to the chorion between 



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