DEVELOPMENT OF THE ALIMENTARY CANAL. 675 



appears about the middle of the small intestine, and not at its upper 

 extremity. The material which afterward accumulates seems to extend 

 from this point upward and downward, gradually filling the intestine, 

 and becoming, in the ileuin and colon, darker colored and more pasty 

 as gestation advances. 



The amniotic fluid, during the latter half of foetal life, finds its way, 

 in greater or less abundance, into the stomach, and thence into the 

 intestine. Small cheesy-looking masses, sometimes found at birth in 

 the fluid contents of the stomach, are seen on microscopic examination 

 to be portions of the vernix caseosa exfoliated from the skin into the 

 amniotic cavity, and afterward introduced through the resophagus into 

 the stomach. According to Kolliker, the downy hairs of the foetus, 

 exfoliated from the skin, are often swallowed in the same way, and 

 may be found in the meconium. 



The gastric juice is not secreted before birth ; the fluids of the stom- 

 ach being generally scanty in amount, clear, nearly colorless, and neu- 

 tral or alkaline. 



Lv-er. The liver is developed at a very early period. Its size in 

 proportion to that of the entire body is much greater in the early 

 months than at birth or in the adult condition. In the fcetal pig the 

 relative size of the liver, is greatest within the first month, when it 

 amounts to nearly 12 per cent, of the entire bodily weight. Afterward 

 it grows less rapidly than other parts, and its relative weight dimin- 

 ishes successively to 10 per cent, and 6 per cent. ; being reduced before 

 birth to 3 or 4 per cent. In man the weight of the liver at birth is also 

 between 3 and 4 per cent, of the entire body. 



The glycbgenic function of the liver commences during fcetal life, and 

 at birth its tissue is abundantly saccharine. In the early periods of 

 foetal life, however, sugar is produced from other sources than the liver. 

 In very young foetuses of the pig, both the allantoic and amniotic 

 fluids are saccharine a considerable time before glucose makes its appear- 

 ance in the hepatic tissue. Even the urine, in half-grown foetal pigs, 

 contains an appreciable quantity of sugar, and the young animal is 

 normally, at this period, in a diabetic condition. The glucose disappears 

 before birth, as shown by Bernard.* from both the urine and the amniotic 

 fluid ; while the liver begins to produce the saccharine substance which 

 it contains after birth. 



Lungs, Uwra.r, and Diaphragm The anterior portion of the ali- 

 mentary canal, which occupies the region of the neck, is the oesoph- 

 agus. It is straight, and, at first, very short ; but it subsequently 

 increases in length, simultaneously with the growth of the neighbor- 

 ing parts. As the oesophagus lengthens, the lungs begin to be devel- 

 oped by a protrusion from its anterior portion, representing the com- 

 mencement of the trachea. This protrusion soon divides into two 

 symmetrical branches, which, by subsequent elongation and subdivi- 



* Lesons de Physiologic Experimentale. Paris, 1855, p. 398. 



