io8 EMBRYOLOGY FROM GALEN [pt. ii 



uterus which it coats and to which it is connected but not united by 

 means of the cotyledons". Thus in one sentence Leonardo falls into 

 a mistake in saying that the human placenta is cotyledonous, but 

 at the same time asserts a fact which it took all the ingenuity of the 

 seventeenth century to prove to be true, namely, that the foetal 

 circulation is not continuous with that of the mother, for the placenta 

 is only connected to the uterine wall and not united with it. "The 

 child", Leonardo goes on to say, "lies in the uterus surrounded with 

 water, because heavy things weigh less in water than in the air 

 and the less so the more viscous and greasy the water is. And then 

 such water distributes its own weight with the weight of the creature 

 over the whole body and sides of the uterus." The tendency towards 

 quantitative and mathematical explanations is apparent at once. 



Further notes are, "Note how the foetus breathes and how it is 

 nourished through the umbilical cord and why one soul governs two 

 bodies, as you see the mother desiring food and the child remaining 

 marked (by a given amount of growth) because of it. Avicenna 

 pretends that the soul generates the soul and the body the body. 

 Per errata^'. The child, says Leonardo, secretes urine while still in 

 utero, and has excrement in its intestines; at four months it has chyle 

 in its stomach, made perhaps from menstrual blood. But it has no 

 voice in utero, "when women say that the foetus is heard to weep 

 sometimes within the uterus, this is rather the sound of some flatus . . . ". 

 Nor does it breathe there (on this point Leonardo contradicts him- 

 self). "The child does not respire within the body of its mother 

 because it lies in water and he who breathes in water is immediately 

 drowned." "Breathing is not necessary to the embryo because it is 

 vivified and nourished by the life and food of the mother." Nor does 

 the embryonic heart beat. To us the statement that there is no 

 respiration in the uterus is obviously false, but we mean by the word 

 tissue respiration, whereas in Leonardo's time pulmonary respiration 

 was intended; he was therefore perfectly right in denying that the 

 embryo breathed, as certain anatomists before him had asserted. 



His only reference to the soul runs thus: "Nature places in the 

 bodies of animals the soul, the composer of the body, i.e. the soul 

 of the mother, which first composes, in the womb, the shape of man 

 and in due time awakens the soul which shall be the inhabitant there- 

 of, which first remains asleep and under the tutelage of the soul of 

 the mother which through the umbilical vein nourishes and vivifies 



