REVIEW OF LITERATURE. 13 



LITERATURE ON THE DEVELOPMENT OF THE MAMMALIAN MENINGEAL SPACES. 



The development of the meningeal spaces in mammals has not been studied 

 extensively, and the literature in regard to it is quite meager. Only a very few 

 workers have touched upon the subject except casually. Reford' 47 ), working in the 

 Anatomical Laboratory of the Johns Hopkins University, studied the development 

 of these spaces by the method of injection with india ink. His work unfortunately 

 has never been published, but it has been rather extensively referred to by Sabin' 491 

 in 1912 and by Gushing' 9 ^ in 1914. Their summaries of this work are here included. 



Miss Sabin thus speaks of it : 



"In a study of the arachnoid made by the injection method in the Anatomical Labora- 

 tory of the Johns Hopkins University by L. L. Reford, and as yet unpublished, it has been 

 shown that the thinning out of the mesenchyme around the central nervous system is not 

 haphazard, but that injections of the same stage give the same pattern, and that the form 

 of the arachnoid space changes as the brain develops. That is to say, the arachnoid space 

 has as definite a form as the ccelom, and it never connects with the lymphatics." 



Gushing^ gives the following summary: 



"It was thought that an investigation of the cerebro-spinal spaces in the embryo 

 would most likely shed light on the subject, and some unpublished studies in this direction 

 were undertaken in 1904 and 1905 by Lewis L. Reford in Mall's laboratory in Baltimore. 

 In living pig embryos of various stages low spinal india-ink injections were made either into 

 the wide central canal or into the subarachnoid space, and the embryos were subsequently 

 cleared. It appeared from the course taken by the injection mass that the full develop- 

 ment of the spinal arachnoid preceded that of the intracranial spaces, the impression being 

 gained that the separation of the primitive meninx into its layers occurred later over the 

 cerebral vertex than in the basilar portion of the chamber. Still, I never felt quite con- 

 vinced that the failure of injection of the meninges over the surface of the hemispheres in 

 many of Reford's specimens was not due to the floating up of the brain against its envelopes 

 by the introduction of the injection mass from below. However this may be, it was never- 

 theless apparent that a venous injection of the body of the embryo was often produced, and 

 the impression was gained that a communication existed between the basal subarachnoid 

 spaces and the precursors of the sinusoidal veins of the cranial chamber which empty into 

 the jugulars. If due to an artifact from a vascular rupture, at all events the communication 

 always occurred at the same point. Reford, moreover, in agreement with Cruveilhier, 

 Reichert, and Kolliker, came to doubt the existence of the foraminal opening described by 

 Magendie, believing that the opening was an artifact and that the fluid escaped by seepage 

 through a persistent membrane." 



It is regrettable that Reford's study has not been published, as it represents 

 the only attempt to solve the problems of the development of the cerebro-spinal 

 space by the method of injection. As stated in subsequent sections of this com- 

 munication, his apparent failure to control pressures of injection and to use only 

 granular suspensions is unfortunate. 



In a study of the development of the blood-vessels of the human brain, MaLU 36 ^ 

 noted the ease with which an extravasation into the embryonic arachnoid spaces 

 could be brought about by increasing the pressure in a venous injection. In a 

 specimen of 46 mm. an arterial injection with aqueous prussian-blue resulted in a 

 complete subarachnoid spread, due to rupture of the vessels as they perforated the 



