REVIEW OF LITERATURE. 9 



this theory, but the failure to find the great Pacchionian granulations in infants and 

 in the lower animals caused many workers to reject utterly the conception of the 

 Pacchionian granulations as the functionally active mechanism for the fluid escape. 

 Physiological evidence, however, advanced by HilK 24 ) from intraspinous injec- 

 tion of methylene blue, indicated that the major escape of the cerebro-spinal fluid 

 was into the venous sinuses of the dura, while a slow and minor absorption took 

 place along the lymphatic channels. ZiegleH 57 ), with potassium ferrocyanide intro- 

 duced into the cerebro-spinal space, likewise found that the venous absorption was 

 much greater and more rapid than the lymphatic. Reiner and Schnitzlert 48 ) with 

 the same agent detected the ferrocyanide in the jugular blood-stream after injection. 

 With olive oil these investigators found a similar venous absorption, but with a 

 slowing of the venous blood-stream. Lewandowsky< 33) , also using ferrocyanide, found 

 this salt in the urine within 30 minutes after its subarachnoid injection. Spina' 521 , 

 from observations on freshly killed and living animals, presented somewhat similar 

 evidence of a major venous and lesser lymphatic absorption. Gushing^ suggested 

 a valve-like mechanism of escape of the fluid, his hypothesis being based on the 

 findings after the introduction of mercury into the meningeal spaces. 



Several theories concerning the absorption of cerebro-spinal fluid into the blood- 

 vascular system have more recently been offered. Mott' 41 ), from a study of dilated 

 perivascular and perineuronal spaces, has advanced the idea of fluid-escape by way 

 of the perivascular system into the cerebral capillaries. Dandy and Blackfan^ 10 ), 

 from an analysis of their evidence, consider that the chief drainage of the fluid is 

 into the capillaries of the pia-arachnoid. Opposed to this conception of a major 

 drainage of cerebro-spinal fluid into the blood-vascular system is the view cham- 

 pioned by CathelinW, that the lymphatic drainage is the chief method of fluid-escape. 

 Cathelin's contention of a veritable circulation of the fluid has not received support 

 from other workers. 



Thus it will be seen that since the work of Key and Retzius the trend of opinion 

 has been away from the view that the Pacchionian granulations cany the cerebro- 

 spinal fluid into the venous sinuses. 



In the earlier investigation' 55 ' carried out in the Harvard Medical School the 

 problems of this fluid absorption were attacked in a somewhat different manner 

 than by previous workers. True solutions of potassium ferrocyanide and iron- 

 ammonium citrate, such as have been used in the present investigation, were 

 injected into the spinal subarachnoid space under pressures but slightly above the 

 normal. The animals (dogs, cats, and monkeys) were kept under anesthesia during 

 the period of injection, which was usually continued for several hours. Complete 

 filling of the subarachnoid channels was secured by this technique, provided the 

 injections were continued for a sufficient length of tune. At the conclusion of the 

 experiment the foreign solution was precipitated in situ and blocks were carried 

 through for histological purposes. 



Many of the anatomical findings in this work carried out as outlined are of 

 interest in the present problem. The complete correspondence of the spinal and 



