PROFESSOR TURNER ON THE PLACENTATION OF THE SLOTHS. 87 
that these coiled or bent hairs, instead of in their growth outwards piercing 
the entire thickness of the epidermis, which they might have been expected to 
do if their apices had been directed to the surface, elevate its superficial 
stratum, and, as the hairs lie thickly together, the stratum is pushed before 
them as a distinct continuous membrane. 
In the month of June 1870, my friend Dr Davip CuristIson wrote me an 
account of a gentleman the hair of whose head had appeared in a very singular 
manner. He was born quite bald, and there was no sign of hair till he was 
fifteen months’ old, when a crop of rounded swellings, about the size of a pea 
or less, appeared on the back of the head; the swellings speedily burst, and 
disclosed a little curl rolled up in each. Other similar swellings appeared in 
successive crops on the other parts of the head, which in their turn burst and 
liberated similar locks of curly hair, until the hairy covering of the scalp was 
complete ; and now this gentleman at the age of thirty-three possesses a head of 
strong curly hair. I was not at the time able to give a satisfactory explanation of 
this singular mode of growth of the human hair, but the study of the epitrichium 
in the sloth appears to throw light on it. The hairs undoubtedly had, in this 
person, as their curly form shows, been bent on themselves in their respective 
follicles, and in their growth towards the surface had elevated the outermost 
stratum of the epidermis instead of pushing through it; but as the growth 
was not precisely cotemporaneous over the whole surface of the scalp, the 
whole of the superficial epidermal layer was not, as in the sloth, elevated at the 
same time, but only as much as lay superficial to any particular lock of hair. 
The epitrichium, therefore, was partial and not complete in its character. 
A few words may now be said on the arrangement, within the abdominal 
cavity of the foetus, of the umbilical vessels. The single umbilical vein passed 
to the liver, and the two umbilical arteries diverging from each other extended 
along the sides of the bladder, which was included between them. No trace 
of a urachus could be found. No remains either of the sac of the allantois or 
of the umbilical vesicle were seen either in the cord or at its placental and 
foetal extremities. RRkupotpui had previously seen* in the embryo of B. tridac- 
tylus a single umbilical vein and two arteries, but in these specimens the 
urachus arose from the anterior wall of the bladder nearer the neck than the 
fundus ; and a similar mode of origin of the urachus was met with in A/yrme- 
cophaga jubata and Manis pentadactyla. Von Baer states (op. cit. p. 263) that 
he has also seen in the Tardigrada the urachus attached not to the summit 
but near the neck of the bladder, though in a foetal Dasypus he found the 
occluded urachus arising from the tip of the bladder. In Carus’s specimen 
also the urachus is figured as attached to the anterior wall of the bladder. In 
* Abhand, der Akad. der Wissensch. zu Berlin, 1828, pp. 40, 41. 
VOL. XXVII. PART I. Z 
