292 HiSTOPvY OF 



the nourishment of the one is Icept within the body of the pa- 

 rent, and increases as the embryo happens to want the supply ; 

 the nourishment of the other is prepared all at once, and sent 

 out with the beginning animal, as entirely sufficient for its future 

 Kupport. But leaving this to the discussion of anatomists, let 

 us proceed rather with facts than dissertations ; and, as we have 

 seen the progress of an oviparous animal, or one produced from 

 the shell, let us likewise trace that of a viviparous animal, which 

 is brought forth alive. In this investigation, Graaf has, with a 

 degree of patience characteristic of his nation, attended the pro- 

 gress and increase of various animals in the womb, and minutely 

 marlsed the changes they undergo. Having dissected a rabbit, 

 half an hour after impregnation, he perceived the horns of the 

 womb, that go to embrace and communicate with the ovary, to 

 be more red than before ; but no other change in the rest of the 

 parts. Having dissected another six hours after, he perceived 

 the follicules, or the membrane covering the eggs contained' 

 the ovary, to become reddish. In a rabbit dissected after twend 

 four hours, he perceived in one of the ovaries, three follicules, 

 and, in the other, five, that were changed ; having become, from 

 transparent, dark and reddish. In one dissected after three days, 

 he perceived the horns of the womb very strictly to embrace the 

 ovaries ; and he observed three of the follicules in one of them, 

 much longer and harder than before ; pursuing his inquisition, he 

 iilso found two of the eggs actually separated into the horns of 

 the womb, and each about the size of a grain of mustard-seed ; 

 these little eggs were each of them inclosed in a double mem- 

 brane, the inner parts being filled with a very limpid liquor. 

 After four days, he found in one of the ovaries four, and, in the 

 other, five follicules, emptied of their eggs ; and, in the bonis 

 correspondent to these, he found an equal number of eggs thus 

 separated : these eggs were now grown larger than before, and 

 somewhat of the size of sparrow-shot. In five days, the eggs 

 were grown to the size of duck-shot, and could be blown frooi 

 the part of the womb where they were, by the breath. In seven 

 days, these eggs were foimd of the size of a pistol-bullet, each 

 'hovered with its double membrane, and these much more dis- 

 tinct than before. In nine days, having examined the liquor 

 contained in one of these eggs, he found it from a limpid colour 

 'ess iluid, to have got a light cloud floating upon it. In ten 



