418 ON GENERATION. 



and extremities ; like a painter, she first sketches the parts in 

 outline, and then fills them in with colours ; or like the ship- 

 builder, who first lays down his keel by way of foundation, and 

 upon this raises the ribs and roof or deck : even as he builds 

 his vessel does nature fashion the trunk of the body and add 

 the extremities. And in this work she orders all the variety of 

 similar parts the bones, cartilages, membranes, muscles, ten- 

 dons, nerves, &c. from the same primary jelly or mucus. 

 For thick filaments are produced in the first instance, and these 

 by and by are brought to resemble cords ; then they are ren- 

 dered cartilaginous and spinous ; and, lastly, they are hardened 

 and concocted into bones. In the same way the thicker mem- 

 brane which invests the brain is first cartilaginous and then 

 bony, whilst the thinner membrane merely consolidates into 

 the pericranium and integument. In similar order flesh and 

 nerve from soft mucus are confirmed into muscle, tendon, and 

 ligament; the brain and cerebellum are condensed out of a 

 perfectly limpid water into a firm coagulum ; for the brain of 

 infants, before the bones of the head have closed, is soft and 

 .diffluent, and has no greater consistence than the curd of milk. 



The third process is that of the viscera, the formation of 

 which in the chick takes place after the trunk is cast in outline, 

 or about the sixth or seventh day, the liver, lungs, kidneys, 

 cone and ventricles of the heart, and intestines, all become 

 visible nearly at the same moment ; they appear to arise from 

 the veins, and to be connected with them in the same way as 

 fungi grow upon the bark of trees. They are, as I have already 

 said, gelatinous, white, and bloodless, until they take on their 

 proper functions. The stomach and intestines are first disco- 

 vered as white and tortuous filaments extending lengthwise 

 through the abdomen ; along with these the mouth appears, 

 from which a continuous canal extends to the anus, and con- 

 nects the superior with the inferior parts. The organs of 

 generation likewise appear about the same time. 



Up to this period all the viscera, the intestines, and the heart 

 itself inclusive, are excluded from the cavities of the body and 

 hang pendulous without, attached as it were to the veins. The 

 trunk of the body presents itself, in fact, like a boat undecked 

 or a house without a roof, the anterior walls of the thorax and 

 abdomen not being yet extant to close these cavities. 



