Franklin P. Mall ' 5 



ordinary India ink into the ventricle of a live embryo with a hypodermic 

 syringe. The ink spreads at once throughout the central canal of the 

 brain and cord and escapes through the medial opening of the fourth 

 ventricle and fills the spaces of the arachnoid of the whole brain and cord. 

 From the cord the ink extended for a short distance along the main 

 trunks of the spinal nerves. In the larger embryos the ink invariably 

 flowed freely from the mouth of the pig as soon as all of the arachnoid 

 spaces had been filled. After hardening the specimens in formalin, razor 

 sections showed that it had reached the mouth through the Eustachian 

 tube. It had entered the middle ear along the trunks of the seventh and 

 eighth nerves. In younger embryos (5 cm. long) the fluid came out of the 

 mouth in only half of the tests, while in the smallest ones injected 

 (3 cm. long) it did not come out of the mouth at all. 



In all of these tests the India ink or the Prussian blue should have 

 passed over into the veins were the communications with them free. In 

 all instances the pigs were still alive or just dead when the tests were 

 made, for it is known that extravasations take place with the greatest of 

 ease after the embryo has been dead for some time. While in. these tests 

 injections could be made with ease from the vein^ into the arachnoid 

 spaces, but not in the opposite direction, in embryos still alive it was 

 found that in no instance would an injection into the artery pass into the 

 arachnoid spaces. The live embryo may be injected using its own heart 

 to inject the India ink. If the uterus is kept warm the embryo will 

 remain alive for an hour or longer, giving ample time. The ink is to 

 be injected directly into the liver with a hypodermic syringe and then 

 by means of gentle massage or by gravity it is forced into the heart, 

 which gradually pumps it all over the body. The arteries to the brain 

 fill slowly and the granules pass over into the veins'. If at this time the 

 embryo is cooled the heart will stop, thus giving a single injection of the 

 arteries. If it is continued, the veins will fill through the capillaries, 

 vrhich confuses more or less. Yet this double injection is desired in this 

 test, for the result is always the same : in no instance is there an extrava- 

 sation into the arachnoid space. In case too great a quantity of ink is 

 injected into the liver, it is forced directly into all of the veins of the 

 body and then the ink granules will leave the veins and enter the arach- 

 noid spaces. If the injection of the arteries and veins of the brain is 

 made through the arteries, using the embryo's heart to do the pumping, 

 all of the granules remain within the blood-vessels, showing conclusively 

 that there are no free communications between the vessels and the arach- 

 noid spaces. When the granules do leave the spaces by injecting them 

 directly into the veins, we must conclude that artificial openings are 



