164 OBSTETBICAL PHYSIOLOGY. 



Fosition of the Fcetiises in Multijjle Pregnancy. 



The relative position of the young in the uterus in the cases already 

 briefly alluded to, is important to remember. With regard to each 

 other, it may be said that they usually occupy four different positions : 

 1. Each foetus may be isolated and enveloped in its own proper mem- 

 branes ; 2. If there are two foetuses they may have a common envelope 

 in the chorion, and otherwise have a second separate sac ; 3. Both may 

 be developed in the same cavity and the same amniotic fluid, their 

 membranes being common, and no partition existing between them ; 

 4. One foetus may be contained within the other by " inclusion," as in 

 some of the monstrosities of which \Ye will speak hereafter. It may be 

 necessary, however, to state that the included foetus may be contained 

 in the abdominal cavity of the other individual, constituting deep and 

 ahdominal inclusion ; or it may be enveloped in a subcutaneous tumour 

 ■ — when it is superficial and cutaneous. 



In the first variety of gestation, the envelopes, where they are in 

 contact, adhere together by means of fine connective tissue; the placentae 

 are often confounded (in Ruminants), or united by a kind of membran- 

 ous connection, though their circulation remains distinct. In such a 

 case the young may be expelled from the uterus together — a frequent 

 occurrence in the Goat, according to Eainard ; but more commonly, 

 after the birth of the first foetus, the uterus contracts on itself, enclosing 

 the remaining progeny, which may not be born until some days after 

 — long enough sometimes to give rise to the belief that it is a case of 

 superfoetation. This apparently prolonged retention of the second foetus 

 is generally due to the fact that the first is expelled prematurely, 

 because of the excessive distention experienced by the uterus ; this 

 organ, having thus got rid of its embarrassment and become relieved, 

 can then maintain the second foetus until the usual time expires. An 

 illustrative case is given in the Memoires de la Societe du Calvados for 

 1831-32. A Mare gave birth to a dead Foal after four months' gesta- 

 tion, and at the ordinary time a living Foal. 



If one of the Foals dies in the uterus, the other, being contained in a 

 separate envelope, may continue to live and grow. In somewhat rare 

 cases, the dead foetus remains in the uterus, becomes desiccated, and 

 is not expelled until the birth of its companion at the usual period ; or, 

 which is more common, it acts in the uterus as a foreign substance, the 

 presence of which is irritating, and by inducing contractions of that 

 organ it is extruded, while the living foetus is retained and grows until 

 the normal time for delivery. 



The foetus that has died during pregnancy may be kept in the uterus 

 for a long time, through close adhesions existing between that organ 

 and the placenta. A case is on record in which a foetus was retained 

 in this manner for two years. Eainard gives an instance of a Mare 

 which retained a dead foetus for a year ; the animal was then fecundated 

 again, but having died while pregnant with the second Foal, an exami- 

 nation of the uterus was made, and the two foetuses were found — the 

 first being mummified. 



Death of the foetus in these multiple cases appears to be due, either 

 (1) to the stronger vitality of the one which lives, and which, by attract- 

 ing to itself a larger share of nutriment, starves the other ; (2) to the 

 too considerable increase in volume of one foetus, which compresses and 

 atrophies the other ; (3) or to the separation of the foetal from the 



