August 4, 1916] 



SCIENCE 



147 



reason that I believe it to be essentially dif- 

 ferent from the method of formation of 

 blood-vessels. 



Again in the eye there are two cavities 

 having an entirely different development. 

 Posterior to the lens is a space filled with 

 fluid, which begins not by a hollowing out 

 of tissue-spaces in mesenchyme, but as a 

 definite differentiation of a primitive vit- 

 reous body by the retina. In the formation 

 of this body the mesenchyme is only sec- 

 ondarily concerned. On the other hand, 

 the history of the aqueous chamber of the 

 eye is analogous to that of the formation of 

 the cerebro-spinal system of tissue-spaces. 



Along the pathway of the blood-vessels 

 of the central nervous system are special 

 chains of tissue-spaces, lined by an indefi- 

 nite mesothelium, but arranged in suffi- 

 ciently definite lines to have received the 

 name of peri-vascular lymphatic spaces. 

 These spaces, however, have no relation to 

 lymphatics and should be called perivascu- 

 lar tissue-spaces. Along the nerves also are 

 chains of spaces which can be injected in 

 the embryo, and which may be termed 

 perineural spaces. Similar chains of con- 

 necting spaces have been injected by 

 Lhamon 4 along the course of the Purkmje 

 fibers of the heart. Besides these very in- 

 teresting special systems of tissue-spaces 

 there is a group of great spaces which is 

 still better known — namely, the great serous 

 cavities of the body. These cavities, which 

 form as a dilatation of spaces in the mesen- 

 chyme, have also a definite embryological 

 history, a definite cellular wall of meso- 

 thelium, and a special very scanty content 

 of fluid. 



In order to analyze the relation of the 

 general tissue-spaces and of these special 

 systems of large tissue-spaces which de- 

 velop out of the general ones, it is neces- 

 sary to submit them all to some type of ex- 



i Lhamon, E. M., Amer. Jour, of Anat., Vol. 13, 

 1912. 



periment. Fluids containing a suspension 

 of minute granules or true solutions whose 

 location can be detected subsequently by 

 the precipitation of granules injected into 

 these various spaces give widely and aston- 

 ishingly different results. Weed has car- 

 ried out a very interesting series of experi- 

 ments of injections into the subdural and 

 subarachnoid spaces. In these experi- 

 ments he. injected a solution of potassium 

 ferrocyanide and iron ammonium citrate, 

 at the same time withdrawing an equiva- 

 lent amount of cerebro-spinal fluid, to 

 eliminate phenomena due to pressure. He 

 found that when the granules of Prussian 

 blue were precipitated by an acid-fixing 

 agent, they were in the meshes of the arach- 

 noidal villi, within the cells of the nests of 

 mesothelium at their tips and within the 

 dural sinuses. On the other hand, when he 

 produced a cerebral anemia by bleeding, the 

 fluid was sucked into the special and very 

 important tissue-spaces that surround the 

 nerve-cells. These experiments demon- 

 strate conclusively that the central nervous 

 system has a special system of tissue-spaces 

 beginning, one might say, with the spaces 

 surrounding every individual nerve-cell of 

 the brain, extending into the subarachnoid 

 area and draining not by lymphatics, but by 

 another special system of absorbents — ■ 

 namely, the arachnoidal villi — into the 

 cerebral sinuses. "Wegefarth 5 has shown 

 that the anterior chamber of the eye has a 

 similar system of absorbents, the pectinate 

 villi. These lead to the canal of Schlemn, 

 a vein analogous to the cerebral sinuses. 



"When injections are made into the peri- 

 toneal cavity the results vary widely, ac- 

 cording to the nature of the fluid injected. 

 As a matter of fact our knowledge of this 

 important subject is far from complete, but 

 it has been shown that certain true solu- 

 tions are absorbed by the blood-vessels. On 



s Wegefarth, P., Jour, of Med. Research, Vol. 

 31, 1914. 



