SECT, i] EMBRYOLOGY IN ANTIQUITY 71 



and origin of the embryo", says Aristotle. This conception of cor 

 primum vivens, ultimum moriens (a phrase never used by Aristotle 

 himself), has henceforward a long and tortuous history, which has 

 been described by Ebstein and others. 



Aristotle goes on to describe the membranes of the mammalian 

 foetus with its umbilical cord: "The vessels join on to the uterus 

 like the roots of plants and through them the embryo receives its 

 nourishment. This is why the embryo remains in the uterus"; not 

 as Democritus thought, so that it might be moulded into the maternal 

 shape. The embryo "straightway sends off the cord like a root to 

 the uterus ". He carefully notes, as if the conception of axial gradients 

 was existing deep down in his mind, that the cephalic parts of the 

 embryo are formed first. "The greater become visible before the less ", 

 he says, "even if some of them do not come into being before them. 

 First the parts above the hypozoma" (a term more or less corre- 

 sponding to "diaphragm") "are differentiated and are superior in 

 size, the part below is both smaller and less differentiated. This 

 happens in all animals in which exists the distinction of upper and 

 lower, except in the insects." Aristotle gives as his explanation of 

 this a teleological argument: "This is why the parts about the head 

 and especially the eyes appear largest in the embryo at an early 

 stage, while the parts below the umbilicus, as the legs, are small; 

 for the lower parts are for the sake of the upper and are neither 

 parts of the end, nor able to form it". 



Embryonic growth is thus described by Aristotle: "The homo- 

 geneous parts (tissues) are formed by heat and cold, for some are 

 put together and solidified by the one and some by the other .... 

 The nutriment oozes through the blood-vessels and the passages in 

 each of the parts, like water in unbaked pottery, and thus is formed 

 the flesh or its analogues, being solidified by cold, which is why it 

 is dissolved by fire. But all the particles given ofT which are too 

 earthy, having but little moisture and heat, cool as the moisture 

 evaporates along with the heat, so they become hard and earthy in 

 character, as nails, horns, hoofs, and beaks, and therefore they are 

 softened by fire but none of them is melted by it, while some of them, 

 as egg-shells, are soluble in liquids. The sinews and bones are formed 

 by the internal heat as the moisture dries, and hence the bones are 

 insoluble by fire like pottery, for like it they have been as it were 

 baked in an oven by the heat in the process of development. . . . The 



