235 
AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 
mixed with a small quantity of water, twenty-four hours before it was employed. In 
the first case, the fluid was obtained when the temperature of the atmosphere was 
51° Fahr., and afterwards sunk to 49°Fahr., but had again risen to 51° Fahr. at the 
time of the experiment. When examined with the microscope, immediately before it 
was used, the fluid still contained a quantity of very active vibratile spermatozoa, and 
also an abundance of spermatozoal cells, still in course of development. This fact 
seemed to afford an explanation of the cause of the efficiency of the fluid for so great 
a length of time, spermatozoa being liberated from the cells during the whole period. 
Thus the fact of the prolonged fecundity of this fluid seems to confirm, instead of 
oppose the conclusion arrived at, — that, the more mature the fluid is before its 
removal from the body, the more efficacious it is, but only for a given extent of time, 
since it is then composed almost entirely of very active spermatozoa, with but very 
few cells of development. Spallanzani, as formerly mentioned*, found that the fluid 
of the foetid terrestrial Toad {Bufo calamital) at a high temperature of the season, 
70° Fahr. to 73° Fahr., at which this species spawns in Italy, had lost its fecundatory 
influence at the end of six hoursT ; but that in the temperature of an ice-house, 
40° Fahr. it retained its efficacy for twenty-five hours;}:. Further, that when the fluid 
was preserved in the testes of the dead animal, at the temperature of the season 
mentioned, it became effete in nine or ten hours; but that it continued to be effica- 
cious, when retained in those organs in the temperature of an ice-house for thirty- 
four hours. Again, he found that the fluid of the green aquatic Frog {Rana esculenta), 
when mixed with a large quantity of water, and placed in an ice-house, the tempera- 
ture of which he gives at 3^ Reaum. (39*87° Fahr.) retained its fecundatory property 
for thirty-five hours §. But it must be borne in mind, with regard to these observa- 
tions, that the species of Toad {Bufo), pair later in the season, and at a higher 
temperature than those of the Frog; and also that the fluid employed by Spallanzani 
in all his experiments, was obtained by vivisection, either from the testes or the 
vesicles; and no doubt contained, as in my experiment just mentioned, many unde- 
veloped cells; and, consequently, not being fully matured, retained its influence 
longer than it would have done, under the same circumstances, in its perfect con- 
dition. 
But Prevost and Dumas ||, in some experiments made to ascertain the length of 
time during which the fluid of the species they experimented on, — the Rana esculenta, 
—retains Its fecundatory property, observed that it was efficient at twenty four hours, 
although removed from the body and preserved during that time, in a temperature 
that varied from 18 to 22 cents., or from 64' to 71° Fahr.^ This result, differing so 
much, in regard to temperature, from the results formerly arrived at by Spallanzani, 
in regard to the Frog, and from the majority of those since obtained by myself, may, 
I think, in great part be accounted for in the fact that, like the Toads, the Rana 
* hoc. cit. p. 212. t Dissertations, &c.. vol. ii. p. 169. t Loc. cit. p. 169. § hoc. cit. p. 194. 
II Annales des Sc. Naturelles, tom. ii. 1824. ^ Loc. cit. p. 140. 
MDCCCLIII. g r 
