GENERATION AND DEVELOPMENT fit 



discoloration with fcetal faeces, or meconium. The amniotic fluid 

 contains proteins, mucin, urea, sugar, lactic acid, keratin, and 

 some salts. Besides these there are also portions of hoof^ 

 epithelium, etc., derived from the foetus. The source of this 

 fluid is probably by transudation from both the foetus and 

 mother. Indigo blue injected into the vessels of the mother 

 tinges the amniotic fluid, though it does not stain the foetal 

 tissues. The function of the amniotic fluid is protective to mother 

 and foetus. The latter lies on it as on a water-bed, and during 

 parturition it assists in dilating the os and lubricating the maternal 

 passage. 



The Allantois grows out from the body of the embryo at the 

 future umbilicus. The part within the body forms the bladder, 

 that outside it forms a sac which, in the mare, completely envelops 

 the amnion (Fig. 249), but in ruminants only partly so (Fig. 250). 

 The bladder and the cavity of the allantois are connected by a 

 funnel-shaped canal in the umbilical cord known as the urachus. 

 The remains of this may be seen in the adult as a scar on the 

 fundus of the organ. The fluid found in the allantois is derived 

 from the foetal urine. In the first instance it is colourless or 

 turbid, later on it becomes brown in tint. This fluid contains 

 urea and a substance alied to it, allanton, also albumin, sugar, 

 lactic acid, and certain salts. The allantois is the organ of 

 respiration, and to a Tmited extent of nutrition. During early 

 foetal life the vascular wall of the allanto's is able to bring the 

 b'ood of the embryo sufficiently near to that of the uterus to 

 effect an exchange of gases. Later on, as we shall see (p. 716), 

 it furnishes the villi which penetrate into the walls of the uterus 

 through the chorion. 



Floating in the allantoic fluid of the mare, or attached to the 

 wall of the sac, are certain peculiar masses termed hippomanes ; 

 their origin and use are quite unknown. It is usually con- 

 sidered that these bodies, which may be multiple, are found in 

 the foal's mouth at birth, but we are assured* that this is a 

 fallacy. Further, these bodies are contained in the allantois sac, 

 whereas the foetus lives in the amnion. Hippomanes have also 

 been observed in the cow. -f 



The Chorion envelops the two previous coverings. Through 

 the umbilical cord it forms the vascular connection between 

 the foetus and the mother, while the villi on its surface project 

 themselves into the mucous membrane of the uterus, not through 

 the medium of a decidua as in the woman, but directly into the 



* Mr. T. B. Goodall, F.R.C.V.S., Christchurch. 



f It is a curious fact that even at the present day, in some country 

 districts, hippomanes are sought for in virtue of the properties they have 

 been supposed to possess from time immemorial — viz., for use as love 

 philtres. 



