Utcro-gestat.ion in Tvy<^on Bleekeri. 421 



running into the bases of the villi ; the contraction of the 

 circuhir fibres, tlie bundles of which curve into the bases of 

 the individual villi, would chi<dly slujrten the villi, while thft 

 contraction of the longitudiiuil fibres would chiefly compress 

 the villi together, both actions serving equally to squeeze 

 out the milk from the glands, which, as we shall presently 

 see, make up so large a part of the villi : outside the sub- 

 mucosa is (3) a thick layer of muscular fibres in an encircling 

 band, (4) an equally thick layer of longitu linally-arranged 

 muscular fibres, and (5) a loose fibrous coat in wliich many 

 large blood-vessels run. 



§ 3. The Secretory Uterine Villi, or Trophonemata. 



For these Professor Wood-Mason and I have elsewhere 

 used the term troj)honemata (or ''nursing filaments"), to 

 denote their milk-secreting function, since the word " villus," 

 in its associations with human physiology, has now come to 

 connote the very opposite function of absorption. They vary 

 in length, in the specimen under description, from half an inch 

 to an inch and a quarter, the usual length being about three 

 quarters of an inch ; in breadth they range from about J^- inch 

 near the base to V^ inch near the tip ; and in thickness they 

 are about ij^y inch through the centre, and about ^^ij of an 

 inch through either margin. 



They are thus quite flat throughout, and are distinctly 

 spathulate at their free end. They usually arise separately 

 and are unbranched ; but often two or three, and sometimes 

 as many as twenty, are found to branch from a single stout 

 peduncular base. Kuuning longitudinally up the centre of 

 each, in strong relief, is a cylindrical swelling which, as will 

 presently be seen, is the single central vein. 



"When a trophonema is stained (in carmine) and examined 

 under a low power wdiat first arrest attention are the blood- 

 vessels. Running along the edge on each side is seen (1) an 

 arteriole which at the tip, without any subdivision, becomes 

 simply confluent, so that the lateral marginal framework of 

 the trophonema is a long narrow arterial loop. 



In the concavity of this loop, coursing down the middle of 

 the trophonema, is (2) a large vein, half as broad again as 

 either of the arterioles ; it is only at the tip of the tropho- 

 nema that the vein shows any subdivision into aflSuents. 



The arterial loop and the vein come clearly into view on 

 deep focusing ; a superficial focus displays (3) a dense 

 polygonal meshwork of capillaries over the whole surface of 

 the trophonema. 



