544 Proceedings of the Royal Society 
I have hitherto spoken of the shedding of maternal tissue along 
with the foetal during the act of parturition. But, to prevent mis- 
conception, it may be well to state that, as indeed has been pointed 
out by Owen,* by Ercolani,f and by myself, | in a memoir pre- 
viously submitted to this Society, if not during parturition, at least 
afterwards, all placental mammals are deciduate; for in the pig, 
mare, and cetacean, “ during the period of involution which follows 
parturition, it is obvious that great changes, either from actual 
shedding of portions of its substance, or from degeneration and 
interstitial absorption, must take place in the constituents of the 
crypt-layer before it can be restored to its proper non-gravid con- 
dition.” 
In the ruminants also, although the epithelial cells may be 
the only constituent of the uterine mucosa which is shed during 
the act of parturition, yet, after that act is accomplished, the thick, 
vascular, spongy tissue of the maternal cotyledon must disappea x 
before the uterus can assume its normal unimpregnated aspect. 
It will be observed that in this communication I have given to 
the term deciduate a more extended signification than has usually 
been attached to it by anatomists. It has been customary to con- 
sider a placenta as deciduate, only when both the epithelium and 
the sub-epithelial vascular maternal tissue are parted along with 
the foetal villi. § But it appears to me that even when the epithelial 
lining of the crypts only is shed, the placenta should be regarded 
as deciduate, inasmuch as there is a shedding of maternal struc- 
ture, though, of course, in an inferior degree to one in which the 
sub-epithelial vascular tissue is also separated. 
3. An Essay towards the General Solution of Numerical 
Equations of all Degrees. By W. H. Fox Talbot, Esq., 
Hon. F.R.S.E. 
* The Anatomy of Vertebrates, vol. iii. p. 727. 1868. 
t Sur les Glandes utriculaires de l’uterus, &c. Algiers, 1869. 
J Trans. Roy. Soc. Edinburgh, 1871. 
g Huxley — Lectures on Comparative Anatomy, p. 10. 1864. 
