EXPERIMENTAL STUDIES ON FETAL ABSORPTION. 49 



(4) diffusion through the amniotic membrane and umbilical cord. It will be of 

 interest to see what light our experiments upon fetal guinea-pig fetuses shed upon 

 these possibilities. 



Absorption of fluid from the amniotic sac by passage into the gastro-intestinal 

 tract. — The passage of fluid into the fetal stomach in the latter half of pregnancy 

 can be demonstrated experimentally in animals by injecting a small quantity of 

 any soluble dye into the amniotic cavity. Of 15 guinea-pig fetuses so injected, 11 

 showed heavy traces of coloring matter in the stomach one hour later. Aft era some- 

 what longer interval the dye appeared in the intestines. It is fair to assume that 

 substances in true solution may enter the fetal circulation in this way. Trypan- 

 blue probably does not, since it is in colloidal solution, and we know that in post- 

 natal life colloidal dyes are not absorbed by the mucosa of the gastro-intestinal tract. 



Absorption of fluid from the amniotic sac by passage into the respiratory tract. — 

 No exact observations upon the respiratory movements of the fetus exist, but 

 everyone who has worked upon pregnant animals is aware that movements re- 

 sembling respiration occur during the latter part of pregnancy. By injecting a 

 colored solution into the amniotic sac it can be demonstrated that amniotic fluid is 

 aspirated into the trachea and lungs. In such experiments the lungs at once become 

 deeply stained. This phenomenon is prettily shown by performing a replacement 

 injection of a 1 per cent solution of potassium ferrocyanide and iron ammonium 

 citrate and after 30 minutes immersing the fetus in acid formalin. Prussian blue is 

 precipitated in the lungs (fig. 3). From these experiments the absorption of small 

 quantities of amniotic fluid through the lower respiratory tract is demonstrated. 

 The failure of previous investigators to describe lanugo hairs, etc., in the respiratory 

 passages does not militate against such a conclusion, since the epiglottis might 

 readily prevent gross material from entering the lungs. 



Absorption of fluid from the amniotic site through the epidermis. — Absorption in 

 this manner does not appear to have occurred in any of the animals injected in these 

 experiments. Whenever trypan-blue was injected into the amniot ic sac the amnion 

 and umbilical cord stained very quickly, but the color stopped abruptly at the 

 junction of umbilical e] >ithelium and the skin at the umbilical ring. The skin of the 

 fetuses, at first uncolored, gradually turned blue as the dye accumulated in the fel al 

 circulation. To determine more exactly that solutions are not absorbed through 

 the fetal skin, in one series of animals potassium ferrocyanide and iron ammo- 

 nium citrate were injected into the amniotic sac. In no instance could precipi- 

 tated Prussian blue be discovered in the epidermis after such injections. The 

 experiments afford definite proof that passage of fluid into the fetus by this route 

 does not occur. 



Diffusion of fluid from the amniotic sac through theamniotic membrane. — If dye- 

 stuffs are injected into the amniotic sac, the fetal membranes and umbilical cord are 

 quickly stained. That this is probably a diffusion phenomenon and resembles 

 transudation, as seen elsewhere in the body (e. g., in the peritoneal cavity), can be 

 demonstrated by means of the Prussian-blue reaction. In 3 experiments a 1 per 



