Utero-gestation in 'Trygon Bleekeri. 421 
running into the bases of the villi; the contraction of the 
circular fibres, the bundles of which curve into the bases of 
the individual villi, would chiefly shorten the villi, while the 
contraction of the longitudinal 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- 
mucoga is (3) a thick layer of muscular fibres in an encircling 
band, (4) an equally thick layer of longitudinally-arranged 
muscular fibres, and (5) a loose fibrous coat in which many 
large blood-vessels run. 
§ 3. The Secretory Uterine Villi, or Trophonemata. 
For these Professor Wood-Mason and I have elsewhere 
used the term trophonemata (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 35 inch 
near the base to z'5 inch near the tip; and in thickness they 
are about ,# inch through the centre, and about s45 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. Running 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 what 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 afiluents. 
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. 
