GENERATION AND DEVELOPMENT 72 i 



The liver is a very active organ in the fcetus, and is abundantly 

 supplied with a mixture of blood, the worst and the best in the 

 body, the best predominating. Early in intra-uterine life the 

 liver begins to secrete bile, which is discharged into the intestines 

 as meconium (see p. 234). 



It is not known how the material passes from the maternal 

 to the foetal tissues ; the blood of the two as previously mentioned, 

 does not come in contact, but active changes occur between 

 them through the villi of the placenta. Protein, fat, carbo- 

 hydrate, and oxygen are received by the fcetus, and carbon 

 dioxide, nitrogenous waste products, etc., delivered to the 

 mother. The nourishment of the mother directly influences that 

 of the embryo, and pregnant animals imperfectly fed can only 

 produce puny offspring. The chemical changes between mother 

 and fcetus in the human subject have been dealt with by P. Barr,* 

 who shows from the nitrogen interchanges that the pregnant 

 woman has a greater power of extracting from her food all the 

 material required for the growth and development of the fcetus, 

 and that at the end she has a balance to her credit. He con- 

 siders, in the matter of nutrition, that a woman stands to gain, 

 and not to lose, by pregnancy. That material may pass from 

 mother to fcetus is proved by the bones of the embryo being 

 stained if madder be administered to the parent. Yet it is known 

 that the placenta, under other circumstances, is an efficient filter 

 for certain pathological substances, and that the tuberculous 

 mother does not convey tuberculosis to the fcetus. It has been 

 suggested that the passage of water, salts, and sugar, from mother 

 to fcetus may occur by diffusion, the passage of fat and protein 

 being perhaps connected with special enzymes. The presence of 

 glycogen in all the embryonic tissues points to it as an important 

 material in the nutrition of the fcetus. Gradually, as develop- 

 ment proceeds, the glycogenic function becomes largely centred 

 in the liver and placenta. 



Uterine Milk. — If the villi of the chorion be separated from 

 the tubular depressions of the mucous membrane of the uterus, 

 a fluid may be expressed, known as ' uterine milk.' This is par- 

 ticularly observable in separating the fcetal and maternal cotyle- 

 dons. Uterine milk is of a white or rosy-white colour, creamy 

 consistence, and contains proteins, fat, and a small proportion 

 of ash. Examined microscopically, it is found to contain 

 globules of fat, leucocytes, rod-like crystals, and structureless 

 masses of protein. The use of the fluid is for the nourishment 

 of the embryo, and in the mare, cow, and sheep the uterine 

 glands take a prominent part in providing-nourishment through- 



* British Medical Journal, October 28, 191 1, p. 11 18. 



46 



