718 



UTERUS AND ITS APPENDAGES. 



devoid of symmetry ; from all parts of their 

 surface spring numerous short pullulations, 

 which render them knotty and uneven. 



Every villus is composed of two distinct 

 parts, viz. an outer leathery sheath, and an 

 inner softer and vascular structure, which is 

 contained within the former like a finger en- 

 cased in a glove. The distinction between 

 these two structures is not easily observed, 

 except in parts where the outer sheath has 

 been accidentally broken off, leaving the more 

 pulpy internal substance exposed. Or in cases 

 where the placenta has become stale by keep- 

 ing for a few days, when the inner portion by 

 shrinking has retired from the end of the vil- 

 lus, so that a small interspace has been here 

 left (fig. 485. b). 



When a terminal tuft so prepared is viewed 

 by transmitted light, under slight compression, 

 the outer case is seen to consist of a trans- 

 parent non-vascular structureless membrane, 

 embedded in the substance, or attached to the 

 inner surface of which are numerous flattened 

 spheroidal cells, forming generally a single 

 layer. In the apex of a growing tuft, or 

 forming a distinct bud projecting from its 

 extremity, may be often observed a group of 

 similar cells which appear to be passing off 

 from a spot in the centre of the mass.* These 

 cells perform important parts in the growth 

 and offices of the villi, which will be presently 

 noticed. 



The internal portion (Jig. 485. b) consists 

 of a soft and pulpy structure which envelopes 

 the blood-vessels of the villi. In its substance 

 also are embedded numerous cells of a similar 

 nature to those observed in the structure- 

 less sheath. 



Termination of the foetal vessels. The ar- 

 rangement and terminal divisions of the blood- 

 vessels within the villi varies considerably 

 according to the age of the placenta. The 

 following distribution is observed from the 

 third to the sixth month (fig. 485. ). Each 

 villus contains one or more arteries and veins, 

 together with numerous capillaries. The ar- 

 teries pass up the centre of the stem, and 

 divide into branches according to the number 

 of the terminal subdivisions. Within these 

 the branches split up into numerous capilla- 

 ries, which present various forms of arrange- 

 ment, in some parts resembling Malpuihian 

 bodies, and in others the arrangement of pul- 

 monic capillaries. From these capillaries the 

 blood is collected by veins which pass back 

 through the tufts accompanying the corre- 

 sponding arteries. All these vessels, with 

 their subdivisions, are enveloped and sup- 

 ported by the pulpy granular substance that 

 forms the interior of every villus (fig. 585. b). 



Towards the end of pregnancy, the true 

 capillaries of the villi gradually disappear, so 

 that in a placenta at term the blood-vessels 

 present the condition accurately described by 

 C. H. Weber and Goodsir. A single vessel 

 generally enters each terminal tuft, and after 



* J. Goodsir. Anatomical and Pathological Ob- 

 servations, 1845. 



Fig. 485. 



- 



a, terminal villus of a foetal tuft, from a placenta 

 of six months. The arteries, veins, and capillaries 

 are minutely injected. The latter, which disappear 

 towards the end of gestation, are here very abun- 

 dant. The arteries and veins occupy the centre, and 

 the capillaries the surface, of the tuft, immediately 

 beneath the non-vascular sheath. The nucleated 

 non-vascular sheath is shown at b, separated from 

 the internal softer structure in which the vessels 

 ramify. (Ad Nat.) 



forming an open loop, it returns again, either 

 dividing within the villus, or leaving it as it 

 entered. Or a single vessel may enter, and 

 retire from two or more villi, before it termi- 

 nates in a principal vein. Many modifications 

 occur in the forms of the loops, which may be 

 simple, compound, wavy, or much contorted, 

 and in parts varicose.* 



Such, then, are the structures belonging to 

 the foetus which are brought into contact with 

 the maternal blood in the interior of the pla- 

 centa, viz. the portion of chorion that forms 

 the floor of the placenta, and the tufts or villi 

 which spring from its surface. The office of 

 the former is simply mechanical in confining 

 the maternal blood to its proper course, and 

 preventing rupture of the organ ; the latter 

 constitutes the potential portion of the pla- 

 centa. 



On the other hand, the sole parts belonging 

 to the mother, the existence of which can be 

 anatomically demonstrated in the substance of 

 the placenta, are formed out of the decidua. 



The decidua. A general description of this 

 membrane, as it forms the roof of the placenta, 

 and sends off dissepiments into its substance, 

 has been already given. It only remains to 



* These are the only terminations of the fcetal 

 vessels of the placenta which have been hitherto 

 described. The true capillary system disappears 

 towards the end of gestation, and apparently, on this 

 account, has escaped the attention of observers, as 

 far as I am aware, except Schrceder van der Kolk, 

 who, in his recent work, has described and figured 

 them in a placenta of three months. Scanzoni also 

 (Lehrbuch der Geburtshilfe,^. 99.) reproduces the 

 figure of Meckel and Gierse, in which the capilla- 

 ries have evidently been injected ; but this is given 

 as an example characteristic of a dropsical placenta, 

 and not as representing a normal state. 



