226 
MR. NEWPORT ON THE IMPREGNATION OF 
snake (Matrix torquata) are not affected by acetic acid, but he makes no reference to 
its action on those of the Frog. 
4. Gum-Arahic. — A thick solution of gum appears to act on the spermatozoa me- 
chanically only, and almost immediately deprives them of motion by the obstruction it 
opposes to them. When a minute drop of spermatic fluid is placed in the midst of 
one of gum solution, and covered with talc, those spermatozoa which have become 
mixed with the gum cease to move instantly, and remain with the tail and body coiled 
in various directions ; while others at the edges and in the midst of the fluid, where 
they are less mixed with gum, still move feebly for a few seconds, but become motion- 
less as the gum collects around them. 
These circumstances will better enable us to understand the following experiments, 
the object of which was to endeavour to learn how far the influence of the sperma- 
tozoa, and the act of impregnation of the ovum partake of a chemical or of a mecha- 
nical nature ; and also will help to determine the length of period of contact requisite 
for impregnation. 
The following experiments bear on these inquiries : — 
Potass experiments. — SetV. March 25,1850. Atmosphere 48° Fahr. Water 46° Fahr. 
No. 1. p.M. 1^ 40“. — Fifty-four ova were passed from the Frog on a dry surface, 
and were instantly bathed with recently-obtained impregnating fluid mixed with 
water; and at the lapse of fifteen seconds were washed by means of a hair-pencil 
loaded with the solution of caustic potass before mentioned ; after which the eggs 
were again washed freely with water. 
No. 2. p.M. l'^ 45™. — Thirty-nine ova were treated in precisely the same way, except 
that the interval between the application of impregnating fluid and the solution of 
potass was only five seconds. 
The ova were removed, after the first day, to a room in which the average tempera- 
ture was about 60° Fahr., and at the end of the eighth day twenty-one embryos, ad- 
vanced to near the end of the fourth period of development, had been produced in No. i, 
and two embryos, at a similar stage, in No. 2. This, at first thought, appeared to be an 
extraordinary fact, seeing that the solution of potass so quickly decomposes the sper- 
matozoa, and even renders the ovum sterile, as was afterwards found ; but, on exami- 
nation of the details, the experiments admit of explanation -.—first, the seminal fluid 
was employed immediately it was obtained, and before the application of the potass, 
which was not used, in the first case, until after a lapse oi fifteen seconds, and in the 
second case, of five seconds ; next, that in both instances the solution of potass was, as 
quickly as possible after its application, diluted and removed by repeated washing of 
the ova with water. Nevertheless, these experiments prove that the ovum becomes 
impregnated very quickly after the application of spermatozoa, and, in these cases, 
even within the short interval of fifteen seconds in the one, and five seconds in the 
other, the difference in the number of embryos produced in the two apparently in- 
dicating the extent in each of the deleterious effect of the solution. 
