1908.] wn the Placenta and Fetus of the Pregnant Rabbit. 265 
it was possible to obtain an accurate and almost complete age-series from the 
14th day to the end of pregnancy. 
As a rule, the material for such investigations is cbtained from the 
slaughter-house, and the age of a fcetus is determined by its size or by its 
weight. Under normal conditions this is a perfectly reliable method, and 
material can be obtained much more easily in this way; but it does not take 
into account the possible occurrence of conditions in which the foetuses have 
an abnormally low weight or an abnormally small size. It will be seen that 
we have met such conditions, and that they have given us interesting and 
suggestive results, which could not have been obtained otherwise. 
The material on which our observations were made is given in the following 
table. 
Table I.—Material. 
Day of gestation ........, 16.| 18. «| 28.|) 29; 
20 a1.) 22. 
5 | 4 
s| s| 6 
Number of foetuses ............ 5 
For the estimation of glycogen, Pfliiger’s method* was used, and the special 
precautions recommended by him for the analysis of small organs were 
carefully attended to.f The maternal and fcetal parts of the placenta, which 
admit of fairly accurate mechanical separation in the rabbit, were analysed 
separately. In the foetus the glycogen was determined in the liver and in 
the rest of the body respectively. The method of procedure was as follows :— 
Immediately after death the abdomen of the pregnant animal was opened 
and the whole uterus removed. Hach sac was opened along its convex border 
and the foetus extracted. Then the foetal placenta was gently pulled asunder 
from the maternal and the membranes were carefully cut away from it. 
Finally the maternal placenta was cut away from the uterine wall with 
scissors, a method which included the zone of separation with its glycogen- 
containing cells in the part for analysis. In the later stages of pregnancy, the 
maternal placenta was detached from the uterus, and the two parts of the 
placenta had then to be separated from each other. In the rabbit there is no 
intergrowth between maternal and fcetal tissues, but the mechanical separa- 
tion is not quite perfect, some of the maternal peninsule that extend down 
between the feetal columns being left attached to the foetal placenta. All the 
maternal placentze were then weighed and afterwards placed together in a 
100-c.c. flask, to which a heated solution of caustic potash (60 per cent.) was 
* Pfliiger, ‘ Piliiger’s Archiv,’ vol. 93, 1903, p. 163. 
+ Pfitiger, ‘ Pfliiger’s Archiv,’ vol. 111, 1906, p. 307. 
