DEVELOPMENT OF UNGULATA. 73-5 



cord the inner layer of the allantois is reflected. The vessels of 



* 



the outer layer branch and spread themselves over it, becoming 

 capillaries in the clusters of short villosities, and thereby brought 

 into the requisite contact with the maternal capillaries in the 

 similarly arranged decidual growths, for the interchange and 

 reception of the materials and elements concerned in foetal nutri- 

 tion. The mucous laver of the allantois lines about half of the 



V 



amnio-chorionic interspace. Towards the latter period of gesta- 

 tion, the renal excretion of the foetus passing from the bladder 

 along the urachus, deposits near the allantoic orifice of that tube 

 a thick fluid of a reddish colour, of an urinous odour, and which 

 contains uroerithrin and hippuric acid. The small oval masses, 

 from the size of a pea to that of a hen's egg, /, sometimes loose 

 in the allantoic cavity, sometimes adhering to its inner surface, 

 are inspissated parts of the allantoic fluid ; they have received 

 a special attention from the fanciful import once assigned to 

 them under the name ' hippomanes.' The chorion, being 

 moulded in great degree upon the uterine cavity, is produced 

 into two ' cornua,' but they are not co-extensive with those of 

 the uterus. The multiplication of the vascular surface of the 

 chorionic cornua by fine and deep plica? indicates the degree of 

 the placentary function assigned to these prolongations. In fig. 

 575 the foatus, m, at about the tenth month, is shown, enveloped 

 in the amnios, n n : the entamniotic part of the navel-string, o, p, 

 is continued to q, r, where the entallantoic part begins, and the 

 allantois is reflected from its urachal pedicle. The eudochorionic 

 part of the allantois is seen at s, s\ a portion of the exterior of the 

 chorion at t : y is part of the left uterine horn ; z is the ovary. 

 The gestation of the Mare is eleven months and a few days : 



O v 



she brings forth standing, and is fertile to the fifteenth year, 

 rarely to the eighteenth. The horse is mature at the fourth year, 

 and its average or usual term of life is thirty years, with fair 

 usao-e. The Ass brings forth during the eleventh month of precr- 



5 O O J. O 



nancy. The milk appears at the tenth month : in very rare 

 cases the ass may have twins. The Mare emits a whitish ad- 

 hesive secretion, ' per vulvam,' during the period of heat. The 

 temporary maternal modification of the uterine lining does not 

 come away with the foetal membranes at birth, but is either ab- 

 sorbed or passed off with the lochia. The usual smooth surface 

 of the folds of the uterine lining is restored about six months after 

 parturition. 



1 The true nature and position of these bodies were made known by Daubenton, in 



ccxc". 



