488 ON GENERATION. 



the common name of hare-lip for the deformity. In the deve- 

 lopment of the human foetus the upper lip only coalesces in 

 the middle line at a very late period. 



I have frequently put a foetus the size of a large bean, swim- 

 ming in its extremely pure nutritive fluid within the transparent 

 amnion, into a silver basin filled with the clearest water, and 

 have noted these particulars as most worthy of observation : 

 The brain of somewhat greater consistency than white of egg, 

 like milk moderately coagulated, and of an irregular shape, and 

 without any covering of skull, is contained within a general in- 

 vesting membrane. The cerebellum projects in a peak, as in 

 the chick. The conical mass of the heart is of a white colour, 

 and all the other viscera, the liver inclusive, are white and 

 spermatic-looking. The trunk of the umbilical veins arises 

 from the heart, and passing the convexity of the liver, perfo- 

 rates the trunk of the vena portse, whence, advancing a little 

 and subdividing into a great number of branches, it is distri- 

 buted to the colliquament and tunica choroidea in innumerable 

 fine filaments. The sides of the body ascend on either hand 

 from the spine, so that the thorax presents itself in the guise of 

 a boat or small vessel, up to the period at which the heart and 

 lungs are included within its area, precisely and in all respects 

 as we have seen it in the development of the chick. The heart, 

 intestines, and other viscera, are very conspicuous, and present 

 themselves as appendages of the body, until the thorax and ab- 

 domen being drawn around them, and the roof, as it were, put 

 on the building, they are concealed within the compages of these 

 cavities. At this time the sides both of the thorax and abdo- 

 men are white, gelatinous, and apparently identical in structure, 

 save that a number of slender white lines are perceived in the 

 walls of the thorax, as indications of the future ribs, whereby a 

 distinction is here made between the bony and fleshy com- 

 pages of the cavity. 



I have also occasionally observed in conceptions of the sheep, 

 which were sometimes twin, sometimes single, of corresponding 

 age and about a finger's breadth in length, that the form of 

 the embryo resembled a small lizard of the size of a wasp or 

 caterpillar ; the spine being curved into a circle, and the head 

 almost in contact with the tail. In the double conceptions 

 both were of the same size, as if produced at once and simul- 



