108 



TRANSITORY CAVITIES IN THE CORPUS STRIATUM. 



A destruction due to other causes is possible; for example, the imperfect circulation 

 of perivascular cerebro-spinal fluid which may be forming in larger quantities than can be 

 absorbed. A dual source for cerebro-spinal fluid has been shown by Weed (12) as being 

 derived from the choroid plexus and the nervous tissue via the perivascular spaces. Unpub- 

 lished work, undertaken by him in the Anatomical Laboratory of the Johns Hopkins 

 University, shows many interesting facts concerning the circulation of cerebro-spinal fluid 

 in the pig embryo. 



The various inconsistencies, as well as the lack of uniformity in structure, could be 

 explained on the assumption of a slow accumulation of fluid about the vessels of the corpus 

 striatum for a short time and its disappearance as soon as adequate pathways in the menin- 

 ges are established. Such an hypothesis of an accumulation of fluid in the striate body 

 gains support from many of these recorded findings. The invariable association of per- 

 forating blood-vessels with the cavities; the development of the spaces before the meningeal 

 differentiation has proceeded far; the presence of coagulated protein-like contents; the 

 bridging of the spaces by tissue strands resembling those of the adult perivascular canals — 

 these are factors of possible consequence in this suggested origin. From this viewpoint, 

 the accumulation of the intrinsic fluid of the nervous tissue resulted in the initial tissue 

 destruction; further distention with more extensive tissue destruction and invasion of 

 macrophages occurred; then, with a possible drainage outward of this fluid accumulation, 

 the pressure was relieved and the space rapidly filled with the nervous tissue. 



SUMMARY. 



The observations here presented indicate that there occur in the corpus striatum of the 

 human embryo between 15 and 20 mm. in length, two bilaterally symmetrical cavities. 

 The presence in these cavities of cells morphologically similar to the macrophages of the 

 adult and to the Hofbauer cells of the embryonic chorion argues strongly in favor of a func- 

 tional significance. The lateral of these cavities is larger and less completely filled with 

 macrophages than is the mesial. No satisfactory explanation of their presence can be 

 definitely advanced. 



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10 



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