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will speedily show some developement of life. Their putrefaction may 

 be prevented, and themselves animated, by shedding on them the sper- 

 matic fluid, obtained by the process employed by Spallanzani, in his ad- 

 mirable experiments on artificial impregnation, 



It is especially to the labours of this able observer, that we owe what 

 has been unveiled of the mystery of generation, and of the part which 

 each sex bears in this function. It is almost proved., that the male co- 

 operates in it, only by supplying the vivifying principle that must ani- 

 mate the individuals of which the female furnishes the germs; that thus, 

 his part is the least essential. It is not so difficult as may be imagined, 

 to explain upon this system, the striking resemblances which are fre- 

 quently seen between fathers and sons. The imperceptible embryo has, at 

 most, the consistency of a slight viscous glue. Such a body must be ex- 

 ceedingly impressible, and the semen of the male, applied to its surface, 

 must impress on it powerful modifications. The action of the fluid on 

 this yet tender embryo must be like that of a seal, which stamps on the 

 soft wax its own image. The impression is the deeper, the resemblance 

 the more striking, according to the spirit and energy with which the male 

 performed the act of reproduction. 



The seminal fluid may not merely act on the surface of the gelatinous 

 and nearly liquid germ, and modify it externally* but it may penetrate so 

 soft a substance, and impress it on inward changes. It is thus that we 

 are able to explain, not only hereditary likeness, but also hereditary dis- 

 eases. Nevertheless, it does appear, that the interior parts are derived 

 chiefly from the female, while the outward parts are especially influenced 

 by the male; for, when two animals of different species copulate, their 

 mule resembles the sire outwardly, and the dam within. It is difficult to 

 show good reason for the want of the generative faculty in mules. Why 

 are their sexual parts, so well developed, altogether barren? What se- 

 cret defect frustrates their action? And why do certain mules, among- 

 birds, propagate, and in the same manner, hybrid plants, which are real 

 mules, and not quadrupeds ? 



The impregnation of the ovum is effected in the ovarium itself, to 

 which the semen is conveyed, as has been said. The ovum, stirred by the 

 action of the semen, and of the fallopian tubs, detaches itself from the 

 organ which has produced it, and descends into the uterus, by the peris- 

 taltic contractions of the fallopian tube. This canal is susceptible of a 

 retrograde motion. It may be conceived, by considering that having 

 stretched itself, by a real erection, to convey the semen to the ovarium, it 

 must, in its return upon itself, cause a flow of the fluid its cavity contains, 

 in a completely inverted direction*. This retrograde motion, as Nisbet 

 observes, is assisted by a sort of collapse succeding the excitation which 

 coition had produced: for, the experiments of Darwin prove that the 

 weakness of the vessels is the cause of this mode of action in their f>ari- 

 etes. Spongy as the urethra of man, the fallopian tube brings back the 

 ovum from the ovarium to the uterus. The extra uterine foetations afford 

 the proof, that matters are carried on in the manner we have stated. Since 

 foetuses have been found developed, in the ovurium, in the fallopian tube, 

 and,even in the cavity of the abdomen, when the detached ovum has 

 escaped from the grasp of the corpus fimbriatumf, one must admit, that 

 it follows the course which has been described. 



* See the Note in the APPENDIX on this subject. 



f In extra uterine abdominal conceptions, the ovum which the tube could not hold or 



3 D 



