VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 115 



ment there was but little vestige of cavity, consequently the corpora lutea might be 

 considered as perfectly formed. 



§ 2. What is tke proximate cause of impregnation ? — As the effect of sexual 

 communication is so important, it cannot be indifferent to the design of nature, to 

 what part of the uterine system the semen should be conveyed. It admits of no 

 doubt that it either remains in the vagina, passes into the uterus, or else extends 

 its course along the fallopian tubes to be applied to the surface of the ovaries, which 

 it stimulates, and from which the new animal derives its existence ; but whether it 

 be one or other of these, has given birth to more physiological controversy, than 

 perhaps any other operation of a living animal. Those who have entered the lists 

 have ranged themselves either on the side of application of the semen to the ovaries 

 by means of the tubes ; or on that of the inutility of this process. These latter 

 contend for an absorption of this fluid by the vagina, a peculiar excitement of the 

 whole frame as a consequence, of which excitement the changes produced on the 

 ovaries are to be considered the local effects. The advocates for the first opinion 

 allege, that the semen has been seen both in the uterus and tubes, and quote as 

 their authority the observations of Morgagni for the former, and Ruysch for the 

 latter. When seen in this last situation, some have thought that it was conveyed 

 thither by the muscular power of these parts in the manner of a peristaltic motion, 

 beginning at the uterus and ending at the fimbriated termination of the tube ; and 

 when at this last, it was supposed that the semen was applied to the surface of the 

 ovaries, and impregnated them by actual contact. 



Though I shall prove that this hypothesis is altogether visionary, yet prima 

 facie it is far from carrying with it the characters of absurdity. There is nothing 

 repugnant to reason in contending for what analogy seems to favour, particularly 

 when the subject is thought beyond the reach of demonstration or proof. And 

 the analogy favourable to this opinion has probably been taken from the impreg- 

 nation of frogs and toads, in which process we are told, on the authority of Roesel, 

 Swammerdam, and Spallanzani, that the ova are impregnated by the male as they 

 are passing from the body of the female ; and that in water newts the ova are im- 

 pregnated even without copulation. Now here is an appearance of contact between 

 the fecundating fluid and the ova. 



Again, on the other hand, the contact of semen with the ovaries has been 

 thought improbable, from an analogy drawn from the vegetable kingdom ; for ad- 

 mitting the Linnaean doctrine to be true, which contends for a necessity of sexual 

 intercourse in vegetables, it would be difficult to demonstrate to the satisfaction of 

 stern philosophers, that the pollen pervades the pistillum, and stimulates the con- 

 tents of the pericarpium by contact, to the evolution of the germen. Such would 

 deny the contact of semen. The advocates for either opinion then may avail them- 

 selves of analogies suited to their own mode of thinking. It may be said however, 

 and with some colour of truth, that the latter analogy, as being more remote than 

 the former, and as being founded on a principle which some have suspected to be 



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